Volvo 240 Alternator Page

2 4 0 T U R B O . C O M
D A V E ' S V O L V O P A G E

240 Alternator Page
and Mechman Alternator Installation

UPDATED: February 8, 2026 CONTACT

D O M A I N S

Send me an email if you have questions or can contribute to any info here.
CONTACT

NAVIGATE THIS PAGE

Alternator Idler Pulley Bracket Project Page (now in a new separate page)

BASICS: How Do Alternators Work?

Poor Charging BOSCH Alternators
Diagnosing Bosch Problems

DENSO Alternators
can be fitted too

Denso Alternators
INCREASING VOLTAGE

Mechman GM Alternator #1
First Install 2010 in my 240

Mechman Alternator #2 2019

BOSCH Alternators
INCREASING VOLTAGE

V-Belts Can Fail if you over-tighten

GM Delco Alternator Wiring
and INCREASING VOLTAGE

ACCURATE VOLT METER Project

LARGE POWER CABLES

240 V-Belt Size Chart

AGM Batteries
Charging Recommendations

Fitting a UNIVERSAL High-Performance Alternator into a 240

For details on the development of this pulley project, go to my new page: Alternator Idler Pulley Page.

240 Alternator Idler Pulley Bracket for 240 red block B21/B23/B230
for use with a high-performance alternator: CLICK HERE.

Some Basics: How does an Alternator Work?

Here's an entertaining video
https://www.youtube.com/watch?v=zfGm0gZhgCc

What to do about your old
Under-Charging Volvo (Bosch) Alternator

Diagnosing Problems with a Bosch Alternator.

This alternator page doesn't have a lot of diagnosing tips when things break, but there are a LOT of those in my Bosch Voltage Regulator Page.
https://www.prancingmoose.com/AdjustableVoltage.html#failure
This is where you should begin if you're having charging system failure issues.

If you are merely a victim of a typical weak under-charging Bosch alternator, you can stay here and have a look below.

Here's an interesting video of the complete restoration of an old Bosch external fan alternator.
https://www.youtube.com/watch?v=eLgjyJBvYs4

And here's one that's show you a pretty good partial rebuild of a 1988 Volvo external fan alternator.
https://www.youtube.com/watch?v=6o_OrF2S_UA

How about a video showing how to remove your 240 Alternator?
https://www.youtube.com/watch?v=A72pWPYm8yo

Improving the Charge with a BIGGER/BETTER Alternator

SO, WHY WOULD YOU NEED A BETTER ALTERNATOR?

My 1984 242 Turbo originally came with a modest Bosch 55 amp alternator . Can someone explain why such a non-significant alternator was used? A non-turbo 240 got a 70 amp alternator.

In stock form, that tiny 55A alternator was barely adequate from the beginning. Like most small Bosch alternators, it suffered from a significant voltage drop when a moderate load was placed on it, especially at idle (although raising the idle to about 1000 rpm did help). And it also suffered from an even larger voltage drop when it got hot (and of course it sits next to the turbo).

The Volvo B21 (red block) engine was not originally designed to have a turbocharger when it was designed in the early 1970s. The turbocharger was added much later. I guess the Volvo engineers did the best they could. Options are few if you have a flame thrower next to your alternator, unless you want to move the flame thrower or move the alternator. They did neither.

Moving the alternator away from the turbo heat, like Volvo did in a 740, may be simpler for some people. I'll discuss that topic later in this page.
INSTEAD I decided to deal with the alternator in the ORIGINAL 240 LOCATION to see what improvements could be made.

ADJUSTABLE REGULATORS (for BOSCH ALTERNATORS)

Many years ago installing an adjustable voltage regulator helped me live with the poor charging situation by bringing up the OVERALL VOLTAGE OUTPUT, but an adjustable regulator can only do so much for a light-duty 55 amp alternator.
An adjustable regulator successfully increased my beginning (COLD and NO-LOAD) voltage from about 13.5 volts to 14.4 volts. But the adjustable regulator cannot increase AMPERAGE capability and it cannot overcome a HIGH-TEMPERATURE voltage drop that's so damned common with Bosch alternators.
HOT voltage output can DROP by as much as ONE or TWO VOLTS in an old Bosch alternator!

You can read more about the reasons why your alternator has a high-temp voltage drop HERE.

WHAT HAVE OTHER CAR MAKERS DONE TO ADDRESS A HOT ALTERNATOR PROBLEM?

Porsche 944 Turbo

In the mid-1980's PORSCHE ran into a similar problem when they added a turbo to the 944 to make the 944 Turbo. There was not enough room on the exhaust side to add a turbo. There was barely enough room for a manifold. So where did the turbo go??? Have a closer look below.
This 4 cylinder engine is similar to the Volvo engine in that the intake manifold is on the LEFT and the exhaust manifold is on the RIGHT. Unlike Volvo, the Porsche engineers found NO ROOM on the exhaust side to add a turbo. Instead, they ran a pipe from the exhaust manifold, UNDER THE ENGINE, all the way to the intake side and put the turbo under the intake manifold just a few inches behind the alternator! Crazy stuff.

You can feel fortunate there were no German engineers working on the Volvo turbo engine design.

I had a discussion with a Porsche 944 Turbo owner about heat-related voltage drops. Porsche engineers did some extra work to try reducing the heat by adding a LARGE AIR DUCT to bring fresh air into the back of the alternator. This likely helped during highway speeds, but heat was still always a big problem. I don't know if Volvo engineers thought about this, but they would have had a difficult time doing something similar, unless they moved the OIL FILTER first.

CAN COOLING DUCTS BE ADDED TO A VOLVO 240 ALTERNATOR?

Yes, if you're determined enough . . . . I think it would be a great idea for alternator efficiency and longevity. But there isn't really any room behind this 240 alternator below. Adding a shroud or duct would require relocating that oil filter first. That might give some space.

So if the 240 oil filter was to be re-located, maybe there could be room for something like this low-profile cooling shroud. This shroud is Porsche PN 96410640302. I have not tried doing anything like this. If you're inspired to try it, please let me know.

Volvo (Bosch) 55 Amp versus 100 Amp

Alternator Size Comparison

The above photos show a size comparison between a Bosch 55 amp (240 Turbo) and a Bosch 100 amp (740).

Here's the bigger 100 amp Bosch alternator above that I installed in my 242 many years ago (circa 2004).
Before I owned my current 242 Turbo, I did the same installation on my old '84 245 Turbo way back in the 1990s.
I simply wanted something with more amperage, since in both cars I was using up the capacity of the 55 amp alternator and getting poor voltage, especially at idle. This Bosch 100 amp unit came from a later 700 series Volvo I found in a salvage yard. Installing one of these was a popular mod and usually helped somewhat.

HIGHER IDLE SPEED
Since even a bigger 100 amp Bosch alternator may have trouble keeping good voltage at IDLE, you also may want to consider raising the idle speed. An idle speed of about 1000 rpm can help.
The new belt size I used for the Bosch 100a unit was typically about 10 x 950 mm or slightly longer (original 240 belt size was 10 x 925 mm)

140 Amp Bosch Alternator

Wes B. sent me a photo of his alternator, which he installed in his 240. It's a Bosch 140 amp Volvo unit he bought from Ebay seller BNR Parts ebay.com/bnrparts. He has reported that it's performing well and it maintains a hot idle at 14.2 volts.

Volvo 240 Accessory Belt Sizes

Information on factory 240 accessory V belt sizes used to be easier to find, but it seems to have mostly disappeared from many useful sites.
I put this info together many, many years ago for my own 240 uses. I thought I would share it here.

ACCESSORY	Volvo PN	Size	Notes
Alternator	958352, 966908	10 x 925 mm	2 needed. 1976-83 240. Also PN 977260.
Alternator	973536, 973538	10 x 918 mm, 10 x 920 mm	2 needed. 1984-93 240. Also 9.5 x 918mm may be used in most cases. PN for these 9.5 x 918 mm belts as a pair: 973537.
			NOTE for all 240 Alternators: If you're upgrading to a larger alternator which will need more room, such as the Bosch 100A unit, you might try using size 10 x 950 mm or up to the maximum size of about 10 x 975 mm.

AC to PS	967114	13 x 1075 mm	1977-84 240. Also 12.5 x 1075 mm. PS with integrated reservoir.
AC to PS	973535	10 x 850 mm	1985-90 240 with remote PS reservoir.
AC to PS	973535	10 x 850 mm	1991-92 240 with integrated PS reservoir.
AC to PS	977759	11.9 x 835 mm	1993 240 with integrated PS reservoir.

Crank to PS (if no AC present)	966909	10 x 938 mm	1977-89 240.

Crank to AC	967103	13 x 925 mm	1976-84 240. Also PN 978678.
Crank to AC	979631	13 x 975 mm	1985-92 240.
Crank to AC	979277	13 x 938 mm	1993 240.

Here's a good video from iPd on Volvo V-Belt Basics and Identification.
https://www.youtube.com/watch?v=wsJ0ROAv6U4&t=138s

MAKING SPACE FOR THE BIG OIL PRESSURE SENDER

Since the Bosch 100 amp alternator case is physically a lot BIGGER than the old 55 amp alternator, it causes interference with the large 2-wire oil pressure sender found in a 240 Turbo. That brass 45 degree fitting came standard on a 240 Turbo, but the bigger alternator still hits this sender with that adapter unless you can swing the alternator outward farther.

So generally the oil pressure sender needs to be re-positioned to make more room for a larger alternator.

Sometimes finding the room for it needs some new ideas, but if the alternator can be swung out further from the engine (with longer belts) you can be successful. But this isn't always possible.

THESE PICS are from some other 240, not mine, but it shows how TIGHT THAT SPACE is for the oil pressure sender when a big Bosch alternator is mounted.

Ultimately, I dealt with the cramped space a bit differently as you can see in this image above. I mounted a "remote sender" after I had some bad experiences with other options, such as trying some adapter fittings which kept cracking from vibration. There's a longer story to this, but the short version is that this remote method actually worked very well for many years.

Here's a thread that goes over the longer version of this story and this mod in more detail:
https://forums.tbforums.com/t=192788

If you can find enough room, the ultimate position for this sender is shown BELOW, WITHOUT ANY BRASS ELBOW or ADAPTER. This would require a way to move the alternator EVEN FURTHER away from the engine.

Or a physically SMALLER alternator might work (i.e: DENSO: Click Here).

A LONGER Belt? Here's how I found there are limits to a LONGER BELT.

A longer belt MIGHT have helped this installation by swinging the alternator further from the engine, which would make extra room for that oil pressure sender. But then you find that swinging the alternator further out only moves the belts TOO CLOSE to the alternator mounting bracket below.
A longer belt in this situation means the belt is going to hit that bracket. So the longest belt in this situation is probably going to be somewhere close to the 10 x 950 mm I used. That belt is about 25 mm longer than factory.

Ok then. What about a DENSO?

Here's the compact Nippon Denso alternator in a 240.

It has become popular to install this smaller case Denso alternator, which can be found in some later 700/900 models.
It's physically smaller than the above 100 amp Bosch. These Densos can usually be found in 80 or 100 amp capacity. They perform pretty much the same as a large Bosch alternator at idle.
The most positive benefit is that they do fit better. There is more room for the oil pressure sender with this more compact alternator.

Denso alternators found in Volvos are usually either 80 Amp or 100 Amp. They look similar to each other, but you'll notice the 80 Amp units have a SMALL 6 mm lug for the fat red cable. 100 Amp units will have a LARGER 8 mm lug.

Info for SERVICING A DENSO

Here's a page devoted to rebuilding a Denso alternator with more pics: https://www.volvoclub.org.uk/faq/Denso
And a discussion thread on Servicing a Denso Alternator: https://forums.turbobricks.com/t=349853

INCREASING THE VOLTAGE IN A DENSO

What about increasing voltage output for a Denso alternator like this? It's not something I have tried personally, but there now seems to be some interesting videos on this subject. Here's one where the author increased output from 14 volts to 14.7 volts. The video is not in English, but following along is pretty easy.

https://www.youtube.com/watch?v=HRgSHGhcolg&feature=youtu.be

INCREASING THE VOLTAGE IN A BOSCH

This is a video about using diodes to increase voltage in a later (internal fan) BOSCH alternator. It's not something I have tried personally. I've never worked on a BOSCH alternator like this one, so I would consider this EXPERIMENTAL. Make sure you read the video description so you have a good understanding before you burn your car to the ground.
VIDEO DESCRIPTION:

120A Bosch alternator modified to 15.3v. A simple diode mod to give 15.3v instead of the factory 14.5v when charging a single lead acid battery (test only). PLEASE NOTE: This is merely a proof of concept. The diode used in this video is only 3A rated and not enough on it's own for the field current at max load. After the video once fitted back to the engine, I swapped the diodes out to 2 parallel diodes in series (4x 3A diodes in total). This bumped the voltage up to about 15.8v at the alternator. Expected field current is approx. 6-8A max, so a single 3A diode could get very hot and blow quite quickly under heavy load. I must also mention any modification you do to your alternator or vehicle is done so at your own risk and I am not responsible for the result.

https://www.youtube.com/watch?v=2PJ5i9fdbWI

Introduction of the
Mechman Alternator #1

This installation of my first Mechman Alternator was back in 2010**.

**MECHMAN ALTERNATOR #2 was later installed in 2019 and CAN BE FOUND BY CLICKING HERE.

Back in 2010 I finally gave up on trying to make a 100 amp Volvo Bosch alternator work to my satisfaction. Clearly, it was not going to cut it.
The biggest downfall for me was how it charged at IDLE when UNDER LOAD and HOT. When running the air conditioning (with a big electric primary puller fan and a condenser fan), voltage was suffering badly at idle and it became much worse after the alternator started getting HOT. I had begun using a big Ford electric puller fan, first trying a Ford T-bird fan from a salvage yard. I eventually changed to a Lincoln Mark VIII (Mark 8) fan. A Mark VIII can pull up to 40 amps at full speed, but full speed isn't really needed very often. But even a raised idle speed of about 1000 rpm couldn't bring voltage up enough for my happiness.

More info on the big Lincoln Mark VIII cooling fan setup and other electric fan ideas can be found in my Electric Fan Page HERE .

My Intro to Mechman

So, in 2010 I was introduced to Mechman high performance alternators by a Turbobricks member.
I then talked with Mechman and I told them about my low idle voltage. I was assured that a custom unit they would send me would improve voltage at idle by offering more amps at idle. Mechman didn't really have a high-performance Volvo-specific alternator, so they custom tailored a GM Delco style alternator to fit a Volvo.

Skipping ahead: The 2010 Mechman alternator did improve charging at idle and overall output was much better, but it STILL suffered from an annoying voltage drop when it got hot. The voltage drop was not as bad as the Bosch though, but I still had to resort to keeping my idle up a bit higher than normal to keep charging voltage from dropping off below 13V when everything was on.
I began thinking there might NEVER be a real solution for a 240 Turbo with the alternator on the hot exhaust side and I thought I might have to eventually move the alternator to the other side of the engine like on the Volvo 740.

SPOILER UPDATE: August 2019
I learned in 2019 that Mechman no longer offers CUSTOM FIT alternators like the one I bought below. It was customized (machined by Mechman) to properly fit a Volvo red block.
BUT, I have since found there are STILL pretty simple solu tions to make a universal high-output alternator fit your Volvo.
I've added info that should help do this. CLICK HERE.

BOSCH ALTERNATOR VOLTAGE DROPS
With the BOSCH 100 amp alternator, the voltage drop between COLD and HOT with a heavy load at IDLE was:
14.4 volts COLD to 12.4 volts HOT.
A FULL 2 VOLT DROP! Unacceptable.
Also this situation was forcing me to set the idle speed higher than it should be to help keep voltage from going through the floor.
Here's a temperature reading from my exhaust manifold (AT IDLE) a short distance from my alternator.

WHY DOES CHARGING VOLTAGE DROP SO MUCH?

(SPOILER: It's ultimately about the WARRANTY)
The reason is that the design of an automotive alternator, specifically the design and efficiency of the copper windings, has a direct effect on the deterioration of current output as temperatures increase. This is partly due to increased resistance in the copper windings as temperatures increase. This deterioration could be corrected by design, however increased current output always increases internal temperatures even more.
Heat is the biggest enemy to alternator long life,
so alternator engineers needed to compromise and they have simply prioritized the designs of alternators to have the best chances of surviving a WARRANTY PERIOD.
Specifically allowing an alternator to reduce output when it gets hot is the answer to that compromise. So there's really not much else you can do with a standard Bosch automotive alternator if it's getting hot and dropping voltage. Volvo did add a thin heat shield for the 240 Turbo. It probably helped slightly. This is not as much of a problem in cars where the alternator is on the opposite side from the exhaust, like in the Volvo 740 or 940.

Isn't there a temperature sensor in an alternator that helps to regulate current output?
With regard to old Bosch alternators that we find in our old Volvos, the answer is NO. There is no temperature regulation in the alternator or in the voltage regulator (except of course the common deterioration of efficiency with higher temps as mentioned above). There are more modern alternators made now, which have internal temperature sensors, but that never existed for the old Bosch units in a 240 or 740.

What about the battery temperature sensor found in some Volvo 740s?
From 1985-87 some Volvo 740s came with a special voltage regulator, which was connected to a temperature sensor mounted under the battery. See the images below. This sensor was there to measure the battery temperature, not the alternator temperature. Additionally, this system did not compensate for high under-hood temps. It was designed to elevate alternator voltage 0.5 volt when it detected extreme cold ambient temps.

FIRST GM MECHMAN MORE DETAILS (2010)

Here's the Mechman alternator from 2010 compared to the Bosch 100 amp I was using up to that time.
The Mechman used a large case GM Delco style housing. This particular alternator had its case slightly modified by Mechman to fit better in the factory Volvo mounting location (while also using a few spacers). I was told this Mechman unit was created as a one-off 170 amp alternator based on the Delco AD230 (which was reportedly in a 1996-2013 GM truck).
NOTE: An alternator like this is used in cars which DO NOT have an ECM or computer controlling the alternator charge output.
This unit from Mechman had a little custom machining to its case at a mounting location so it would bolt up similar to the Volvo Bosch alternator.
More about the machining modifications Mechman did can be found HERE.

Similar Volvo conversions have been done using GM AD244 and GM DR44 late model truck alternators. The reported benefit is better output at idle, which is something the old Volvo Bosch unit don't do well.

4-POLE ALTERNATOR PLUG INFORMATION

This alternator will have a 4-pole connector for the regulator. Note: The P-L-F-S pin designations below are also sometimes called P-L-I-S.

This connector can be found fully assembled with wire pigtails as PN 110-12046.
If you need the connector housing only or the terminals and seals separately, search for:
Metri-Pack 4-Way connector, Aptiv (Delphi) PN 12186568.
Female terminal 17-20 AWG, Aptiv (Delphi) PN 12048074.
Wire Seal Aptiv (Delphi) PN 15324976.
Sealing Plug Aptiv (Delphi) PN 12059168.

More info: www.dirtydingo.com/ID=108

Here's what the above GM Mechman #1 (from 2010) looked like installed in my car.

The belt size I typically used for the Bosch 100a was 10 x 925 mm or 10 x 950 mm.
I found that if I could swing this Mechman slightly further from the engine, I could eventually fit a 10 x 965 mm.
The limiting factor was always the lower part of the alternator bracket where you can see the belt getting close.

GROUND CABLE When Using a GM Alternator

Attaching a big ground on this alternator was a bit different that the old Bosch.

It didn't come with a ground stud on its case, so the solution (also suggested by Mechman) was pinching a ring terminal against the case underneath as shown here. It turned out to be a good solution as long as that long bolt doesn't tend to loosen over time. I used a good lock-nut on that long bolt to make sure it didn't vibrate loose.

The best charging results with this new (2010 Mechman) alternator came after I added a dedicated 4 GAUGE ground cable and positive cable DIRECTLY from the alternator to the battery. You can see the results of numerous tests in the above mentioned installation thread. I still experienced a pretty significant COLD-to-HOT VOLTAGE DROP using this alternator, but ultimately adding these cables provided the best result so far for any alternator I had tried up to this time.

Using enhanced (LARGER) POSITIVE and NEGATIVE Cables.

The latest version I did on my car uses FAT FINE STRAND, high-flex WELDING CABLE. Welding cable uses very small wire strands, making a large, fat cable much more flexible.

Why do you need flexible cable? I'll tell you why.
My first cable version used large, fat normal strand cable. The vibration and flexing of the fat power cable at the alternator eventually broke the cable at the alternator lug after a number of years and many miles, leaving me stranded and calling for a tow truck. Plan ahead and get better cable.

This illustration ABOVE will give you an understanding of the enhanced power and grounds that are recommended with a high-amp alternator. You might consult the manufacturer of your alternator for a cable size recommendation, but be prepared to be told to make them very BIG. I made this illustration above to show the big dedicated cables (POWER AND GROUND) going directly from the BETTER TO ALTERNATOR and a big cable from the BATTERY TO STARTER. The factory used a cable going between the alternator and the starter. This become unnecessary. Using a cable there was convenient for the Volvo factory, but it's better to ALWAYS use cables directly from the battery to the component.

<<< WARNING NOTE: I don't recommend using one of these inexpensive disconnect devices on your battery when using a high output alternator like this. I had one of these on my negative battery terminal back in 2010. After installing the Mechman I began experiencing some strange intermittent momentary voltage drops when the alternator was under load, such as when the AC was on. It took a while to figure it out and it's detailed in the Turbobricks thread mentioned above. It turned out that this disconnect knob was creating higher resistance in the ground cable circuit and the Mechman was sensitive to it. I removed this devise so that my battery ground was solidly connected.

Dealing with BELT SLIP

Belt Slip is the Unintended Side Effect of a HIGH-PERFORMANCE ALTERNATOR

Have a good look at the belts wrapping around this pulley. There's just a little more than 90 degrees of belt wrap.
The actual belt-to- pulley contact patch is pretty small. But that's how a 240 is designed. This is not very good and it's why the designers added DUAL BELTS.

This was not really a problem back when the weaker 55 amp original Bosch alternator was there, but it became intolerable with a high output alternator.

I found that I needed to tighten the alternator belts much more and then they usually needed more tightening later as they began to wear. I was putting a LOT of stress on my belts. That can cause problems.

BROKEN BOLT

That bolt on the front of the block for the adjusting bracket has been known to break off (it happened to ME).
I've also heard of a few people with broken water pump pulleys (see thread here: https://www.forums.turbobricks.com/t=323223).
Over-tightening a V-belt is just plain BAD. It can also prematurely wear water pump bearings and generally your belts don't last as long as they should. They just wear faster and then they begin slipping again sooner.

MORE ON THE BROKEN BOLT ISSUE WILL CONTINUE LATER IN THIS PAGE.

Belt Failure Concerns from Over-Tightening.

This was NOT an alternator belt. This was a 240 crank pulley to AC compressor belt.
It failed after about 300 miles of use because it was adjusted too tight. The belt didn't actually break, but it did jump off the pulleys after breaking those reinforcing cords.

That long corded string stuff above was the embedded cord in the top-side of the belt. The cord separated from the belt (or maybe snapped from too much tension) and then eventually unraveled. The belt eventually came off the pulleys and I found it sitting in my belly pan. Most of that corded material ended up wrapped around my AC pulley. Once that corded part separated, the belt lost the ability to stay tight. After losing that corded material, the belt became more like a big, soft, stretchy rubber band.

MECHMAN #2

Updated 2019: I Got a New BIGGER/BETTER Mechman

NAVIGATE THIS PAGE

Wiring a GM Mechman

Increasing Voltage in a GM Alternator

PLFS 4-Wire Plug Info

GM Voltage Regulator

In 2019 I installed Mechman #2 in my 242.

This one is physically about the same size as the previous Mechman, but it's much "beefier" on the INSIDE.
This alternator came with a 170 amp 6 phase HAIRPIN STATOR.
According to the literature a bit further below, it's based on a GM Delco CS130D (original to a 1998-2002 GM F-body, i.e.: Camaro).
NOTE: An alternator like this is used in cars which DO NOT have an ECM or computer controlling the alternator charge output.
This Mechman part number was B8206170M (PN B8206 with 170 amps).

The alternator Mechman provided for me was custom prepared by them for a VOLVO.
This means they did some MINOR MACHINING to the case so it would easily bolt up in the Volvo red block mounting location similar to a normal Volvo Bosch alternator. And of course it also got a double V-belt pulley instead of a serpentine pulley, since the 240 uses V-belts.
More on the custom modifications that were done to create this alternator can be found HERE.

UPDATE NOTE about custom Mechman availability: August 2019

In 2019 I learned that Mechman no longer offers CUSTOM FIT alternators to directly fit a Volvo. This customization was done to my alternator. More about this is further down in this page.
So are the custom features really necessary? The answer is NO!
There are great solutions to make a UNIVERSAL high-output alternator fit your Volvo.
I have added info below that will help. CLICK HERE.

Before getting this alternator I had no clue what a 6 PHASE HAIRPIN STATOR was.

Now that I know, I'm here to say that if you upgrade to a high-performance alternator, buy one with a 6 Phase Hairpin stator. There's info below that will show you how different a 6 phase hairpin stator looks and performs compared to a normal 3-phase type.

So, the 6-phase hairpin design looks pretty cool.
. . . but does it actually perform better?
YES IT DOES. Keep reading below.

WIRING a GM Mechman

I've added some information below on how the WIRING is done for this alternator or for ANY GM style alternator with a similar 4-pole plug.

More info below on the P-L-F-S connector.

. Here are a few ways to connect an alternator like this.
You've undoubtedly heard of 1-wire alternators. Forget what you've heard. This is NOT a 1-wire alternator.
A true 1-wire alternator is considered self-exciting and doesn't require an external circuit source to excite charging. The GM CS130D requires an external source to excite it (similar to a Volvo Bosch).
In most OEM systems, this excite circuit is the wire to the dash battery warning lamp, like the Volvo Bosch.
In this example below, a resistor is used instead of a lamp.
Note: P-L-F-S plug pin designations are sometimes called P-L-I-S.

Resistor. 470 Ohm 1/2 W Carbon Film Single Resistor.
www.amazon.com/WWNKYZX7ES9QZMTDZ693
The polarity for a resistor is not specific. A resistor can point either direction.
If you're familiar with the old Bosch alternator, it used the red D+ wire from the dash charge warning lamp to excite the charging. The GM CS130D is not very different. This method above is pretty standard for this type of alternator, which uses this the P-L-F-S plug.
With this method above the “L” (Lamp) terminal is connected to switched 12v, with a resistor in-line to reduce current to the regulator. The resistor will offer a similar effect as a warning bulb, except with this method you will not have a dash warning lamp that will illuminate if the alternator fails. Either way, the resistor is important. Many on-line sources say that if you do not use a resistor on this circuit, you may eventually burn up the voltage regulator.
The 12 volt switched source needs to be powered when the key is in the "RUN" position. This will activate the alternator when the engine begins running. It must be a switched circuit, because if a constant 12v circuit was connected, it would eventually drain your battery after the engine was shut off.

ALTERNATIVE using TWO Excite Circuits

An alternate method of exciting the alternator is shown above. This method offers two redundant ways to excite the alternator. Plus it offers an opportunity to have a normal dash warning lamp if you want one. The lamp used in a dash lamp is normally a very low wattage incandescent bulb (1 or 2 watts). The bulb will offer a small amount of resistance, which will serve protect the regulator in the same way as the resistor method above. The alternator doesn't need very much resistance to excite and a 1 or 2 watt bulb is perfect. Some sources say the minimum trigger to excite might be as low as 1/4 watt.
The only downside to using a bulb to excite the alternator is if it burned out, the alternator may stop charging without warning. Fortunately, this above method also offers a redundant way to excite using the 'F' terminal. The "F: terminal is also connected to switched 12v. No resistor should be used with the 'F' terminal wire.
More info: www.dirtydingo.com/shop/ID=108

.VIDEO: Activation of GM style alternator with P-L-F-S plug.
Here's a video that demonstrates the use of the above 470 Ohm resistor INSTEAD of a bulb.
https://www.youtube.com/watch?v=a3pp448t0U4

Resistor. 470 Ohm 1/2 W Carbon Film Single Resistor.
www.amazon.com/dp/WWNKYZX7ES9QZMTDZ693
The polarity for a resistor is not specific. A resistor can point either direction.

VIDEO: Here's a tricky method designed to BUMP UP VOLTAGE in any GM style alternator that has an 'S' (Sense) terminal.
This method may work for any other alternator which uses an S terminal. This method uses diodes. Mods like this are at your own risk.
https://www.youtube.com/watch?v=qLX-RBcsNrU

In the above video he is using the following resistor and diode below:

Resistor connected to the "L" wire: 470 Ohm 1/2 W Carbon Film Single Resistor.
www.amazon.com/dp/B07QYRRX3L
The polarity for a resistor is not important. It can point either direction.

Optional DIODE connected to the "S" wire: 1N5404 Rectifier Diode 3 amp 400V.
www.amazon.com/BOJACK-Rectifier
The polarity for a diode is important. The silver band needs to point TOWARD the ALTERNATOR.
Here's another video below discussing the above 1N5404 3 amp Diode connected to the 'S' wire where an increase of about 0.3 volts per 3 amp diode is demonstrated (results can vary).
https://www.youtube.com/watch?v=MRoJMv-yMSY

Alternately you may use one or more 1N40001 - 1N4007 1 amp Diodes instead of a 3 amp if you feel like experimenting for different voltage results.
1 amp Diodes are featured in the next video below.

POTENTIOMETER METHOD TO INCREASE or ADJUST VOLTAGE in a GM Alternator
Here's another method designed to bump up voltage output in an alternator with an 'S' (Sense) terminal.
This method uses a 5k Ohm POTENTIOMETER and optional 1 amp diodes. NOTE: Mods like this are at your own risk.
https://www.youtube.com/watch?v=QEIpHnuj6sc

This video above is very brief and explains things rather quickly. I made a diagram below that will help. The 1 amp diodes are optional. He explains that these diodes are in place to offer a default voltage setting that will be ABOVE the normal setting, which only comes into use in case the potentiometer circuit fails. So you could try out one, two or three diodes there to see what that setting would be.

At the end of the above video he says, "This is effectively a $5 external voltage knob, not $80." I think the $80 knob he is referring to is a 5k Ohm potentiometer box that is a ready to use device and sold as the Brand X Voltage Control Knob: https://brand-x-electrical.com/ . If you're looking at ready-made control knobs, that might be a solution.
Or you could consider one from Coventry Car Audio, which offers a control knob with a voltage display: https://www.coventrycaraudio.com/.
If you use one of these ready-made devices, you'll see in their instructions that you can use an optional relay. I DEFINITELY recommend using that relay.

4-POLE ALTERNATOR PLUG INFORMATION
This plug connects to the regulator and would be typically found in a 1998-2002 GM F-body (Camaro), 2004-2005 Buick or Pontiac, and 2001-2006 Cadillac.
Fits alternator part numbers: Denso 104210-3060, 104210-3070, 104210-3300, 104210-4540; GM 15145637, 25697765, 25697766, 25758348, 25759776, 84009369.
Note: The P-L-F-S pin designations below are also sometimes called P-L-I-S.

More info: www.dirtydingo.com/ID=108

DELCO VOLTAGE REGULATOR

If the voltage regulator ever needs to be replaced in this CS130D type Delco alternator, I thought I would add that info here, just in case it becomes useful to you (or me) in the future.
12 Volt, B-Circuit, S-F-L Terminals, 15.0 Voltage Set Point, w/ LRC For Denso Alternators.
Part Numbers: Denso 126600-0030, 126600-0031, GL10031, 104210-330, 104210-454, Transpo IN6003.

Installing a Super ACCURATE Volt Meter.

Anyone can install a volt meter. I've installed many, but this is a bit DIFFERENT.
THIS section will discuss my work in getting a really, really ACCURATE volt meter, after many years of NOT having a very accurate one.
Working toward an extremely accurate volt meter might seem a bit obsessive, but if you've read this page, you can easily come to your own conclusion about THAT.
If you've used the factory 240 VOLTS gauge, like I did for a while, you know it's NOT known for being precise and probably not very CONSISTENT either.

The below info will detail how I did this project in my 240 and the results. I have some suggestions here, but this certainly is NOT the only way to do this kind of thing.
I welcome your comments.

Teaser - Spoiler
You'll see more about this if you keep reading, but what I discovered got my attention.
If you test voltage at the battery or in the dash when your car is idling with LITTLE OR NO LOAD, you'll generally see less voltage than what the alternator is actually putting out. Maybe only a few tenths of a volt less at the battery. A lot less if measured at the dash, possibly 3 to 5 tenths of a volt less at the dash with LITTLE OR NO LOAD. Then if you do the same test WITH A HIGH LOAD (such as with AC running), I have seen a voltage drop of up to 1.5 VOLTS LESS, even though the OUTPUT AT THE ALTERNATOR really did not change at all.

My Volvo originally came with one of these VDO VOLTS gauges. It can help give you a general idea that things are charging or not charging, but you can't tell a whole lot more about your alternator performance.

Over the years I've tried a few of these cheap digital meters.

The most common meters are like this 3-digit LED meter below. They work fine and can found on-line cheap. I prefer a digital meter anyway now, because it tells me sooner if something has changed about my charging system. But is a digital meter like this any more accurate? How do you know? Does it matter where this meter gets the voltage in your car?

And THIS TIME I wanted to step up to a 4-DIGIT LED display (with 2-digits to the RIGHT of the decimal). Four digits for no reason other than preference.

THE KEY TO SUCCESS:

A more DIRECT PATH from the ALTERNATOR for Power AND Ground wires.
Having a 4-digit meter isn't important. This guide works with any voltmeter. This 4-digit unit has three wires instead of two wires. You can see the meaning of that third wire in the diagram below. That's not a super important thing.
You can see below I connected both power wires to the same place.

4-digit meters like this are a bit harder to find if you want one. You can try searching for 4-digit DC volt meter. Having 4-digits does NOT make this more accurate. What makes it accurate is a MORE DIRECT PATH from the alternator to the meter. A typical factory in-dash volt gauge doesn't have a very direct path at all. Not even close (see here about why that "path" is bad).
The factory gauge will have a number of connections between the battery/alternator and the dash. So it suffers dramatically from voltage loss.
This diagram below involves the GM 4-wire alternator I'm using. The Bosch diagram is further below.

The POWER and GROUND PATH in this diagram above from the alternator to the volt meter is pretty DIRECT. The only thing I added in it's path is a standard mini RELAY.
Without that relay, the alternator "S" Sense circuit in this GM type alternator would be active all the time when the car is off. Also the meter would be on all the time. That can drain the battery and it's kinda bad to do that. So the relay is there to activate things when the car is on and running and to shut it all off when the car is OFF.

DIAGRAM for a Volvo BOSCH Alternator? Even easier.
The relay is still used. A relay should be included or your meter will never shut off.

An ALTERNATE connection to the KEY IN Warning Chime can be made below. With this connection the only change will be the volt meter will activate when the key is inserted and will stay activated in all key positions until the key is removed. The reason for choosing this method would be if you want to see the battery voltage before you begin turning the key.

WHY IS THE FACTORY VOLTAGE PATH NOT SO GOOD?

The factory path of the wiring for a 240 volt gauge is by using power and ground in the dash. That dash power comes through a number of different wires and connectors between the battery and the gauge. All those connections will cause a voltage drop.
Here's an example of how COMPLICATED the PATH normally gets for a factory 240 volt gauge.
Beginning at the battery, there's a wire going to a junction block on the inner fender. From there, another wire goes back to the firewall, into the under-dash area, terminating at a pole on the ignition key switch. This is where battery power is switched to ON for things in the dash that don't have full-time voltage. From the ignition switch, aother wire runs to the fuse panel. The circuit will then probably go through a fuse (possibly fuse 13), and then a new wire goes to a multi-pin plug near the instruments. From that plug a power wire is shared by several gauges. Meanwhile a lot of voltage drop has taken place.
NOTE ABOUT CHASSIS GROUND: Using a normal chassis ground in the DASH is fine for most devices, but the same voltage problem can happen for a volt meter with a poor chassis ground. A chassis ground in your dash may not provide as clean a path as a DIRECT ground wire DIRECTLY from the battery or the alternator to the volt gauge. This is why I say it's important to take the power and ground for this meter directly from the alternator..

Is VOLTAGE DROP really such an important thing to eliminate?
Take a few seconds and watch this ONE MINUTE video on Voltage Drop Testing.
https://www.youtube.com/shorts/ORv0eh_aY2A

CONSISTENT READINGS

I mentioned consistency early in this article. Why?
My testing has suggested that volt meter readings can be more consistent when very little load is present, but when load increases, consistency changes, sometimes a lot. We know using power-hungry accessories will pull voltage down in most Volvo 240 systems, but does that always mean the battery or alternator output is being pulled down equally. My tests say NO. This type of inconsistency can fool your volt gauge into registering less voltage than your system has at your battery or alternator.

Here are some photos showing the wiring to my GM type alternator.
The first image below shows the PLFS plug on my Mechman alternator.

The next image below is an Amphenol AT connector for those same wires as they run from the alternator to the right fender. I added this connector for convenience so it's easier to disconnect when I need to remove my alternator.The wires below then go back to the firewall and into the dash. I have a detailed page HERE showing this Amphenol connector if you need to see more about it. These connectors are easy to work with and are waterproof.

This image below is showing the new 4-digit meter installed at the base of my center console. Yes, it's reading 14.77 volts. That's actual alternator output for my Mechman.

COMPARING VOLT READINGS: If I test the voltage at the battery when idling, it generally reads about 1 or 2 tenths of a volt less than this alternator output.
When measuring the voltage coming from the battery to the dash, which suffers from the most voltage drop, it can be 3 to 5 tenths of a volt less than alternator output when NO LOAD is present. A LOT worse, up to 1.5 VOLTS LESS, when there's a HIGH LOAD. So now with this new meter setup showing me the ACTUAL ALTERNATOR OUTPUT at all times, I can rest more comfortably on long trips knowing my alternator is nice and consistent.

MORE GM MECHMAN GENERAL INFO

The GM Mechman I'm using is this one above, PN B8206170M. The '170' in the PN is the amps. The 'M' is a machined finish.

This style alternator is also available in 240 amps and in a BLACK finish, such as the PN B8206240B pictured below.

Note about the alternator POWER OUTPUT lug:
In this photo above you can see the B+ output lug may be pointed to the rear or to the side. I'm using one that's pointed to the rear.
If requested, Mechman offers the option of either configuration.

HAIRPIN STATOR
(This info taken from a MECHMAN page)

6 Phase Advantage

Mechman Elite and S Series alternators employ cutting edge alternator technology not found in other aftermarket alternators. 6 phase hairpin stators make Mechman Elite and S Series alternators fundamentally more efficient than other aftermarket alternators. This new technology and increased efficiency equates to incredible output at extremely low engine RPM, less energy wasted in the form of heat, and more horsepower to the wheels. Also because less heat is being generated, the internal components of Mechman Elite and S Series alternators last longer. This is especially beneficial on turbocharged and/or endurance racing vehicles with high engine compartment temperatures. All Mechman Elite and S Series alternators feature soldered stator and rectifier connections, with epoxy re-enforced stator connections, reducing the chance of vibration failures.

High Pole Count

Mechman Elite and S Series units are built exclusively with precision balanced low-mass rotors that allow them to operate safely at shaft speeds of 20,000+ rpm. This high RPM capability, combined with excellent output at idle, gives the user a much broader operating RPM range, and more flexibility in the size of the crankshaft pulley used. A properly selected Mechman Elite and S Series alternator can even fix low voltage problems caused by using small diameter, or "underdriven" pulley ratios. The higher pole count in the rotor also results in less electromagnetic interference to cause problems with radios and other electronics.

Twin Rectifiers

As a final precaution, Mechman Elite and S Series alternators are constructed with twin high efficiency cooling fans, and twin internal rectifier plates. While other high performance alternators have only one rectifier with 6 diodes. Mechman Elite and S Series units boast 12 press fit diodes with 300% more surface area to dissipate heat. These considerations to cooling airflow and heat dissipation make Mechman Elite and S Series high performance alternators the most durable aftermarket alternators you can buy. If you are experiencing pre-mature alternator failure, intermittent electrical accessory problems, or low voltage at any engine RPM, a Mechman Elite or S Series alternator is the answer!

Parts Comparison: 6-Phase High Output MECHMAN versus 3-Phase
https://www.youtube.com/watch?v=LMB2Rrpz9yg

6 PHASE HAIRPIN STATOR
P E R F O R M A N C E

Here are the dyno specs for this 6 phase alternator, Mechman PN B8206170M. As you can see it puts out 145 amps at idle and 185 amps while cruising.

That sounds impressive but what does that mean in real life?

IT MEANS THIS:
Now, when I first fire the car up cold, the voltage output is ~14.8 volts. As things warm up, it slowly settles to about 14.6 volts.
So then what if I turn on accessories, like EVERYTHING you can think of: AC and high wattage headlights, etc.
With the old 100 amp Bosch alternator, I would see a HOT voltage drop of up to 2 volts.
With this Mechman it STAYS VERY STABLE with a voltage drop of up to about 0.2 volts (measured at the battery), even when HOT and even during hot 900 rpm IDLE!
Alternator voodoo like this has never happened to me before! Certainly never with a Bosch.

ALMOST NO ALTERNATOR VOLTAGE DROP WHEN HOT!
Impossible you say? I would have doubts too if I didn't see it for myself.
So yes, if you can afford it, buy a 6 phase hairpin stator alternator.

And this video shows the fully HOT alternator voltage when getting a full load.
https://www.youtube.com/watch?v=T5c_6JGEplo

While the above reading may seem deceiving, the actual voltage drop measured at the BATTERY is shown below.

IDLE SPEED
I've mentioned in a couple places in this page that sometimes I have increased my idle speed to improve charging. This was an absolute must when I was using a Volvo BOSCH alternator and back then I had to keep idle at 1000 RPM or voltage would drop too low. With a Mechman this can be a subject to pay attention to also, but for me it was not nearly as important because the Mechman charged better at low RPMs.
Every car is not the same. My 1984 240 Turbo factory idle speed is 900 RPM. I typically run my car at about 950. Most non-turbos recommend 750 ±50 RPM. I know some MECHMAN users are running their idle below 700-800 RPM, but I think 700 RPM might be pretty much as low as I would go with a Volvo 4 cylinder and with an alternator like this. You'll probably find there's a certain RPM threshold where charging begins to drops off if you dip too low, so adjust accordingly.

MECHMAN versus Other Performance Alternators
Mechman 6-phase alternators are not cheap, but they have very high quality. Be careful if you begin looking at no-name or Chinese made high-performance alternators. Mechman made a comparison video showing how cheap some of the fake "high-amp" alternators can be:
https://www.youtube.com/watch?v=j5l4z3b2zHA

Mechman has options for adjusting voltage if you need that. I ultimately found that it was NOT needed for my installation, since my alternator stays put at full voltage under all load conditions.
If you're interested in Mechman alternators, you can find them at: https://www.mechman.com/

CS130D Disassembly, Rebuild
If by chance you're playing with GM CS130D alternators, I found the below video, which details the disassembly and rebuilding of one. I found it pretty interesting and decided to put it here in case it becomes useful for someone.
https://www.youtube.com/watch?v=hdK8ZqNvGsc

FITTING A UNIVERSAL HIGH-PERFORMANCE
ALTERNATOR TO A 240

In August 2019 I learned that Mechman no longer offers specially customized alternators made to directly fit a Volvo red block. They do, however still offer a wide variety of alternators, including the same model I bought, but they just don't want to deal with customizing them for a Volvo. It turns out the customizing part was actually pretty minor. I'll show that below in detail. It's not absolutely needed.
So it's certainly still possible to fit a great high-performance Mechman alternator to your Volvo.

When searching for an alternator style you can use, It's my opinion that you should look for something with mounting points similar to the original Bosch. In other words, you might choose something similar to the below LEFT image as opposed to the below right image.

So Mechman chose an alternator configured like this below.

This particular alternator was chosen by Mechman because the mounting points were somewhat close to the Bosch mounting points. Keep in mind that they are somewhat close, not precisely close.
It turns out that SOMEWHAT CLOSE will be just fine for a Volvo.

Then they altered the aluminum case at that top 2 inch thick flange by machining the back surface of that TOP 2 inch dimension. This is where your tension adjuster bracket attaches. They reduced the thickness there from 2 inches to 1.25 inches. There's more detail below, but that machining does NOT really HAVE to be done to fit this unit into a Volvo. I'll show you.
Then of course they also replaced the serpentine belt pulley with a dual V-belt pulley. That's pretty much it for any mods.

The Mechman pictured below left is believed to have originally begun as a Delco AD230 for a 1996-2013 GM truck.
The Mechman #2 that I installed later in 2019 (CLICK HERE) was originally designed from a Delco CS130D for a 1998-2002 GM F-body (Camaro). So If you buy a Mechman alternator or a high-performance alternator from another company, you can use this information as a guide to help you find a model that will fit a Volvo.

Lets discuss the above dimensions.
DIMENSION A is the mounting flange for the alternator to factory engine bracket. Rubber bushings and a long 8 mm bolt (13 mm head) are used. The Bosch alternator fits just right in that factory bracket, but as you can see the Mechman dimension A is 3/4 inch smaller. Spacers were used for the Mechman in my car and you can see that in an image HERE.

DIMENSION B is the thickness of the mounting flange for the top adjuster bracket. This was modified on the above Mechman.
This Mechman originally began with this flange being 2 inches thick (Dimension D). Mechman custom machined the case so this flange was reduced to 1.25 inches thick. That reduction brought Dimension D very CLOSE to the same as the Bosch Dimension B (which is 1 inch thick). This modification worked fine, but as I recall I did still needed to make some sort of adjustment to the top adjuster bracket to deal with the 1/4 inch difference. I think I probably flipped the adjuster bracket 180 degrees or I inserted the rubber bushing on the other side. There are a few tricks like this to make the alignment better on an early bracket. Ultimately it worked just fine.

DIMENSION C is the distance between the two mounting points. The above Mechman is 1/2 inch shorter than the Bosch for Dimension C. This ultimately made NO difference at all.

So, is machining an alternator case really needed?
No! As mentioned above, it's NOT needed.

I did a bunch of measurements and determined that an UNMODIFIED non-Volvo alternator (like a Delco above) can be made to fit very well if your top tension adjuster bracket is MOVED back a bit. The easiest method I know to do that is to install one of my idler pulley brackets, which allows for this very thing.

So if you choose an alternator which has that thicker Dimension B (such as a Delco unit for GM truck or Camaro mentioned above), you COULD go to the trouble of disassembling it and having the case machined like Mechman did. . . . Or if you don't want to do that, and if you are considering using one of my idler pulley brackets, have a look at the below images.

These images above shows the top adjuster bracket mounted in the NORMAL location for an alternator with dimensions similar to the Bosch. So then this configuration worked for me with an alternator that was modified like Mechman did. (NOTE: That's a Bosch 100A in this photo above).

Now have a look at this change below. . . .

This is an early Mechman in these photos ABOVE. It's possible to mount the top tension adjuster bracket to the REAR or BACK-SIDE of the bracket mounting ear as shown.
I have demonstrated this by inserting a spacer at the alternator to simulate a thicker, unmodified alternator flange (Dimension B) with a full thickness of 2 inches, like it was before it was ever machined by Mechman.
So just like that, fitting an unmodified Delco style Mechman or other alternator is possible without a lot of fuss.
And there is STILL a lot of room for the oil pressure sender!

SOME CUSTOMER PHOTOS BELOW.

ABOVE THREE PHOTOS: I received some photos and feedback from a customer who used this Mechman B8206240B alternator, which is nearly identical to mine, except this one has 240 amp capacity and is BLACK in color.
NOTE: This alternator ABOVE was not modified to fit a Volvo. It was installed with the top tension adjuster bracket positioned on the REAR of the idler pulley bracket mounting ear. It fits very well.

Also you can see this alternator has the large OUTPUT LUG pointing to the SIDE, instead of pointing to the rear like mine. Mechman can offer a choice when you place an order.

Also keep in mind that the "CLOCKED" position of the back 4-pole connector plug and output post can be changed or rotated relative to the alternator mounting position.
I discussed this partial disassembly procedure in the following thread beginning at Post #41: http://forums.turbobricks.com/t=350085

V-BELT PULLEYS
When considering an alternator that you think will work, the next important thing to determine is if it can be fitted with a V-belt pulley.
Most alternators for cars made in the last 20 years will probably come by default with a SERPENTINE belt pulley.
V-belt pulleys are widely available for almost any alternator and you just need to make sure there's one available that you can use or there is one that you can customize if a stock one is not available.
The original 240 double V-belt pulley is made to fit 10 mm wide belts.
The below photo shows three different double V-belt pulleys.

The LEFT pulley is an original pulley for a Bosch (Volvo) alternator using 10 mm wide V-belts. This is from an old 100A alternator.

The MIDDLE pulley is for a Delco alternator using 10 mm V-belts. This came on my first Mechman.

The RIGHT pulley is for a Delco alternator using 13 mm wide V-belts. This came on my second Mechman.

The difference does not look very large in the photo, but it might make a difference if use a 13 mm pulley with 10 mm belts. It might be OK, but I preferred to use the correct pulley for the V-belt width if possible. Maybe the different V angle could promote BELT SLIP if it doesn't match perfectly (???). I don't know. I have used a 13 mm pulley before and it seemed ok. If you decide to use a 13 mm belt pulley with 10 mm belts, let me know how it works out for you.

SELECTING A SUITABLE V-BELT PULLEY
Since I became a bit obsessive about a good fitting pulley, this is an issue that I needed to deal with when I installed the latest Mechman #2 in 2019. I'm posting this just to show that sometimes unexpected problems come along and this is how I solved this one.
The above MIDDLE Delco 10 mm pulley (same as this one below) was originally supplied by Mechman with the first Mechman #1 alternator I bought back in 2010 ( based on a Delco AD230 alternator for 1996-2013 GM truck). This pulley worked fine on that early Mechman. The part number for this pulley is 24-1101 (or 241101). It can also be identified as Delco 1846787, 1964758, 1968354, 1970830, or Ford C5AZ-10344-L, C5TF-10A352-K2, C9AF-10A352-C, E4TZ-10344-B, E6SF-10A352-AA, E6SZ-10344-A, GP494, GP617, GP629.
FYI: This type of pulley is also generally characterized by the 13 mm dimension from the back flange to the center of the first groove (refer to the pulley diagram below).

When Mechman shipped the latest alternator #2, which I installed in 2019 ( based on a Delco CS130D for a 1998-2002 GM F-body car), it came with the ABOVE RIGHT Delco pulley, which is made for wider 13 mm belts. That pulley *might* be OK for 10 mm belts, but I was stubborn and decided instead I wanted a proper 10 mm pulley.

The first thing I did was to try to fit the above middle 10 mm Delco pulley (24-1101) on the new Mechman. It did actually go on (the alternator has the same 17 mm shaft diameter), however the shaft length on the new alternator was shorter. It didn't stick out as far. That made it impossible to use that pulley in stock form. The shorter shaft meant the 16.5 mm flange dimension in the ABOVE diagram was a bit too thick and the large nut holding the pulley on could not be threaded on enough. I was getting about 1 turn on the nut. Not good enough.

CUSTOM SOLUTION
The solution I chose was having a 24-1101 (10 mm) pulley custom machined. This means that I had the inner recess cut deeper to reduce the 16.5 mm flange thickness to 12 mm. You can see the difference between this image below and the above one. That solved the problem and allowed me to use the Delco 10 mm pulley. The diagram below shows the MODIFIED dimensions for this pulley.

AND THEN I LATER FOUND THIS PULLEY.
Here's a possible alternate 2-groove pulley I found later, but I have NOT tried fitting one of these.
It's made for 10 mm belts. It has a slightly larger outside diameter, 75 mm instead of 67 mm, but I think it might be worth trying if you would rather not go to the trouble of having a pulley machined/modified. I think this one could possibly be mounted with the addition of one or two washers behind it to get proper spacing out, away from the alternator case, since there is no flange/shoulder sticking out on the back side on this pulley.
This pulley is PN 24-3105 (or 243105). Chrysler PN 5227174 for Chrysler 40/90, 50/120A alternators. Chrysler, Dodge, Plymouth 1987-1989. The center hole is made for the same 17 mm shaft diameter, so I think it may fit with some luck.
If you try one of these, please let me know how it works out.

Here's a good selection of 2-groove pulleys, all machined from cold-rolled steel .
alternatorparts.com/2-groove

AGM BATTERY INFO

For my Volvo I use the below AGM battery, which is made for O'Reilly by East Penn Manufacturing..

This is the Super Start Platinum from O'Reilly Auto. The Volvo 240 uses Group Size 34, which uses the above specifications.
An AGM battery means it's constructed using Absorbed Glass Mat, which is superior in design to an old school flooded lead acid battery.
I picked this battery because it's made by East Penn Manufacturing, who has been known for making the revered Deka battery line. I've been very happy with this type of AGM in my car for many years.

ALTERNATOR CHARGING VOLTAGE
The Mechman alternator I use typically keeps alternator output between 14.6 and 14.7 volts when things are good and hot and stable. This seems to be OK for this AGM Battery and I think it's not excessive. Most high performance AGM battery manufacturers warn against overcharging when using a battery charger (sometimes warning to not charge above 14v). Charging with a battery charger is not the same as an ALTERNATOR maintaining a charged battery. Most published recommendations for alternator charging are between 13.8 and 14.8 volts, while some I've seen recommend up to about 14.6 volts. I've seen recommendations from Interstate Batteries for not over 15 volts for an AGM.

Keep in mind any of these recommendations always comes with temperature variables, so try not to take them as absolute. For example, you can see how recommended charging voltages will change dramatically depending on ambient temperature in XS Power Battery guidelines. This PDF below used to be in their pages, but no longer, but I saved it:
https://www.davebarton.com/pdf/BATTERIES_XS_Power_PSseries_Instructions.pdf

Most guidelines will agree that ALTERNATOR charging below 14 volts is getting very close to insufficient for an AGM battery.

Here's a very detailed PDF document from East Penn Manufacturing on GEL versus AGM. They offer both, but a GEL battery is not the same as AGM. The recommendations between them are quite different for charging voltage too.
https://www.davebarton.com/pdf/Batteries_East_Penn_Gel_or_AGM.pdf
This image below is from page 11.