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 Mod Page

     UPDATED: August 12, 2019                       CONTACT       
D  O  M  A  I  N  S
davebarton.com PrancingMoose.com 240Turbo.com
Payments and Policies
New Items
Cool Volvo Products 240 Modes & Fixes
                  Stickers Volvo
                  SteeringWheel Labels
Volvo Wire Harnesses Volvo Harness Parts, Terminals, Connectors.
Volvo Prancing Moose Stickers Other Car Stickers Volvo Relays and Sensors.
Volvo 960
                  coil harness repairs.
Volvo Underhood, Body and Chassis Sticker and
                  Labels Other Car Stickers 740, 760,
                  780 Turbo Boost Faces Volvo Custom
                  Black or White Faces.
240 Black
                  Door Vinyl Stripes. Volvo 240 Window Scrapers 740, 940 odometer repair gears and instructions. Volvo 240 Odometer Repair Gears
                  and Instructions.
Prancing Moose, Volvo R-SPORT Horn
                  Buttons, replica Alpina horn buttons Wheel Center Cap Overlays. Volvo Group A Racing Articles Classic Auto Air Condition Conversion 240 Hydraulic
                  Clutch Volvo Adjustable Voltage
Volvo Meet Photos. Electric Fan Diagrams Volvo
                  tropical fan clutches SoCal Area Salvage Yards Side Markers on 240s and 740s Modified 240s
Unleaded Race Fuel at the
B26FT Stroker
                  Vacuum Diagrams
Dave's 245
                  Specs Used Volvo Stuff
240 big brakes
                  apparel from Cafe Press
Prancing Moose Apparel from Cafe
                  Press 240 Modes & Fixes Favorite Links

Bosch Alternator
Denso Alternator
Mechman Alternator
Belt Failure
Belt Slip
Alternator Idler Pulley
Send me an email if you can contribute to this info.

What to Do with Your Old Under-Charging Alternator
Here's an interesting YouTube video of a complete restoration of an old Bosch external fan alternator.

And here's one that's show you a pretty good partial rebuild of a 1988 Volvo external fan alternator.

How about a video showing how to remove your 240 Alternator?

Improving the Charge with a Bigger/Better Alternator
My 1984 242 Turbo originally came with a modest Bosch 55 amp alternator. In stock form, it was barely adequate from the beginning and like most Bosch alternators, it suffered from a significant voltage drop when a moderate load was placed on it, especially at idle.  And it suffered from a larger voltage drop when it got hot (and of course it sits close to the turbocharger). 

The Volvo red block engine was not originally designed to have a turbocharger. It was added much later and the Volvo engineers did the best they could. Not much can be done if you have a flame thrower next to your alternator, unless you want to move the flame thrower or move the alternator.  Moving the alternator may be easier.  maybe I'll discuss that topic later. 
For now I will deal with the alternator in the original location.

Installing an adjustable voltage regulator helped me live with this situation by bringing up the overall voltage output, but an adjustable regulator can only do so much. The adjustable regulator successfully increased my beginning (COLD) voltage from 13.8 volts to 14.4 volts.  But the adjustable regulator could not increase amperage capability of the small alternator and it cannot overcome a high-temperature voltage drop (except of course in part by increasing the overall beginning cold voltage setting). The voltage output could drop by more than a volt when the alternator became HOT.

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

In the mid-1980's Porsche ran into a similar problem when they added a turbo to the make the 944 Turbo. I had a discussion about similar heat-related voltage drops with a Porsche 944 Turbo owner.  Porsche engineers did something extra to reduce the effect by adding a large cool air duct to bring air into the back of the alternator. This likely helped some during highway speeds, but it was still a big problem.
Volvo engineers would have had a more difficult time doing something like this, since the oil filter was in the way.

Volvo (Bosch) 55 Amp versus 100 Amp Alternator Size Comparison


<<< Here's the bigger 100 amp Bosch alternator I installed in my 242 many years ago (circa 2003). Before this car, I did the same install on my old '84 245 Turbo back in 1997. I simply wanted something bigger and badder than what I had, since in both cars I was using up the capacity of the original 55 amp alternator and getting poor voltage. This 100 amp unit came from a later 700 series Volvo I found in a salvage yard. This was a popular mod back then.
The belt size I used for the Bosch 100a unit was in the range of 10 x 925 mm to 10 x 950 mm.

<<< Since the 100 amp case is physically BIGGER than the old 55 amp alternator, it causes interference with the large 2-pole oil pressure sender found in turbo 240s.  The brass 45 degree fitting came on 240 Turbos.
<<< So generally the oil pressure sender needs to be re-positioned to make room.  Sometimes finding the room for it is difficult, but if the alternator can be swung out further from the engine (with longer belts) you can be successful. <<< THESE PICS are from some other 240, not mine, but it shows how tight the space is for the oil pressure sender when a big alternator is put in there.
Ultimately, I dealt with the cramped space a bit differently by doing a remote sender installation.  Here's a thread that goes over this in more detail: https://forums.tbforums.com/showthread.php?t=192788

<<< If you can find enough room, the ultimate position for this sender is shown here, WITHOUT THE BRASS ELBOW, but this would require some planning to get the alternator further away from the engine and/or a small alternator is needed.
<<< A longer belt MIGHT have helped this installation by swinging the alternator further from the engine, which would make a little bit of extra room for that oil pressure sender.  But then you find that swinging the alternator further out only moves the lower part of the belt too close to the alternator mounting bracket (where that lower long bolt and bushing is).  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 that I used.

What about a DENSO?
<<< Here's the Nippon Denso alternator in a 240.  It has become popular to install this smaller frame alternator found in later 700/900 models. It's physically smaller than the above 100 amp Bosch. These Densos can be found in 100 amp or higher capacity, yet they don't really perform any differently or better than a large Bosch at idle. They do fit better though.

There is usually a bit more room for the oil pressure sender with this more compact alternator.
Here's a page devoted to rebuilding a Denso alternator with more pics: https://www.volvoclub.org.uk/faq/ElectricalDensoRebuild.htm
And a discussion thread on Servicing a Denso Alternator:

2010 Installation
In 2010 I decided that the 100 amp Volvo Bosch alternator was not going to cut it.  The biggest problem was how it charged at idle. When running the air conditioning (with a big puller fan and dual condenser fans), voltage was suffering badly at idle and much worse after the alternator started getting HOT. I had begun using a big Ford puller fan, starting with a Ford T-bird fan and eventually settling on a Lincoln Mark VIII fan that pulls 40 amps at full speed.
More on this big fan setup can be found in my
Electric Fan Page HERE.

With the Bosch 100 amp alternator, The difference between cold and hot voltage when adding a heavy load at IDLE was from 14.4 volts COLD to 12.4 volts HOT, a full 2 volt drop!  Also it was forcing me to set the idle speed higher than it normally should be to help keep voltage from going through the floor.
Here's an IDLE SPEED temperature reading from my exhaust manifold a short distance from my alternator.


You've noticed how much voltage drops when your alternator gets hot, right? This is not something that car alternator manufacturers want to talk about.  The reason is that automotive alternators are specifically engineered so that they reduce output when they get hot.  This is because heat is an enemy to an alternator and it can be a common reason for failure.  So alternator engineers designed their alternators to have the best chances of surviving the WARRANTY PERIOD.  Engineering them to reduce output when they get hot is the answer to that. So there's really not much else you can do with a standard automotive alternator if it's getting hot and dropping voltage. Volvo did add a thin heat shield for the 240 Turbo.  It probably helped a little. This is not as big a problem in cars where the alternator is on the NON-exhaust side, like in the Volvo 740 or 940.

In 2010 I was introduced to Mechman high performance alternators by a Turbobricks member.  I then talked with Mechman and I was assured that the custom unit I was buying would improve voltage at idle.
Mechman didn't have a Volvo alternator, so they custom tailored their GM style alternator to fit the Volvo.
Skipping ahead: The Mechman alternator did improve charging at idle and overall output was much better, but it STILL suffered from a 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.
I began thinking there might NEVER be a real solution for a 240 Turbo with the alternator on the 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.

I did this custom Mechman alternator installation in 2010. 
I began a discussion thread in Turbobricks back when I did this, which helped me solve some issues. 
That thread is here:

<<< Here's the Mechman alternator compared to the Bosch 100 amp. It uses a large case GM Delco style housing that has been set up to correctly fit in the factory Volvo mounting location (while using a few spacers). I was told this Mechman was a one-off 170 amp unit based on the Delco AD230 with some custom machining to its case so it would bolt up similar to the Volvo Bosch.

<<< Here's the Mechman unit installed. There was not a lot of room for adjustment. Probably a little more than the big Bosch offered though.

The belt size I used for the Bosch 100a unit was 10 x 925 mm or 10 x 950 mm
I swung this Mechman slightly further from the engine and the
new belt size used was 10 x 965 mm.
<<< Attaching a ground was a bit different on this alternator.  It didn't have a ground stud on its case, so the best solution (also suggested by Mechman) was pinching a ring terminal against the case underneath as shown here. It's a good solution as long as that 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 alternator came after I added a dedicated 4 gauge ground cable and positive cable from the alternator directly to the battery.  You can see the results of numerous tests in the above mentioned installation thread.  I still experienced a significant cold to hot voltage drop using this alternator, but to date it was the best result so far for anything I had tried.   

<<< WARNING: Don't use one of these disconnect devices on your battery when using a high output alternator like this.  I had one of these disconnect devices on my negative battery terminal.  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 disconnect knob was creating some resistance in the ground cable circuit and the Mechman was sensitive to it.  I tossed it in the trash and made sure my battery ground was solidly connected.

Unintended Side Effects of a High-Performance Alternator:
Dealing with Belt Slip
<<< Back to this photo:  Have a good look at the belts wrapping around that pulley.  There's just a little more than 90 degrees of belt wrap and the actual belt-to-pulley contact patch is small.
This was not a problem back when the weaker Bosch alternator was in there, but it began to become more of a problem with a high output alternator. 
I found that I needed to tighten the alternator belts much more when adjusting.  Putting too much pressure here can cause problems.  That bolt in the block for the adjusting bracket has been known to break off and I had seen a few people with broken water pump pulleys (see thread here: http://www.forums.turbobricks.com/showthread.php?t=323223). It can also prematurely wear out your water pump bearings and generally your belts don't last as long as they should. They just wear faster and then they will begin slipping again sooner.


Belt Failure
Why Over-tightening is Bad
<<< This is a 240 crank to AC belt.  It failed after about 300 miles of use because I had adjusted it too tight.  The belt didn't actually break. 
That long corded string stuff 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 pulley 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 is more like a big, soft, stretchy rubber band. 

Update 2019:
Got a New Bigger/Better Mechman
NOTE: In August 2019 I learned that Mechman no longer offers alternators to fit Volvos.
You can email me if you have questions.

<<< I got a new one.  It's actually physically about the same size as the previous Mechman, but it's much "beefier" on the INSIDE. This is a 170 amp 6 phase HAIRPIN STATOR alternator.  Before getting this alternator I had no clue what a hairpin stator was.  Now that I know, I'm here to say that if you upgrade to a high-performance alternator, buy one like this.
I wish someone had educated ME about hairpin stators BEFORE I BOUGHT THAT LAST MECHMAN!
There's info below that will show you how different a 6 phase hairpin stator looks compared to a normal.

  Yes, the hairpin design looks pretty and it looks like it means business,
but does it actually perform better?


Here's the dyno specs for my new 6 phase alternator, Mechman PN B8206170M.  As you can see it puts out up to 145 amps at idle. 
That sounds impressive but what does that really mean?

It means THIS:  When I now first fire the car up cold, the voltage output is 14.8 volts (stable at idle and any RPM). As things warm up, it slowly settles to about 14.7 volts. So then if I start turning on accessories, like EVERYTHING: AC and high wattage headlights, etc. (I have 400 watts of lights), guess what.  It STAYS STABLE AT 14.7 volts! Even at IDLE when hot!

Remember this thing sits near the turbo, right? 
Still at 14.7 volts!  NO 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.
I made a couple short videos.
This one below shows the cold start voltage for this alternator: https://www.youtube.com/watch?v=YPIoiIaRiFc

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

I've been told by a couple people that Mechman alternators are good, but that DC Power alternators are better.  Are they?  I have no idea, but I do know that when no one seemed to care about old Volvos, Mechman did!
What can DC Power provide to fit a Volvo 240? Volvos are not mentioned in their site.  If you know, let me know about it.

Mechman 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 also has options for adjustable voltage if you need that. I found that it was NOT needed for my installation.
If you're interested in alternators like this, you can find them at:

Up next:  
Seriously Dealing with that Belt Slip
I began a discussion thread on this project in 2019: http://forums.turbobricks.com/showthread.php?t=350085

CHIEF SYMPTOM: The 240 alternator design doesn't offer enough BELT WRAP (belt to pulley contact) for an alternator that can push a very heavy load.  The Volvo engineers added a second belt, which makes it better, but if you exceed the grip capacity for those belts, it's just not going to work. 

After installing this new Mechman high-performance alternator in 2019 I found a need for more belt grip.  This was an immediate problem when running my AC (along with my big Lincoln Mark VIII puller fan and dual condenser pusher fans).

I found I could improve grip a little by getting longer belts and swinging the alternator further from the engine.  This photo to the left was taken with 10 x 975 mm belts, which were put on after I found it seemed to grip slightly better than shorter belt sizes.  I thought I might have had a solution until these new belts would no longer grip at idle under load after a few thousand miles of use.  This situation was forcing me to drastically increase belt tension in an effort to maintain more grip.

The worst slipping was always at idle when there was a heavy load on the alternator.  I could always tell when slipping was happening, even before hearing any squealing, because I could see my voltage drop from 14.7 to the mid 13s. Revving the engine just made the belts squeal.  Fixing it was a matter of switching off the AC and trying again after I was driving.

If you look at this photo, you'll notice there really isn't room to swing the alternator any further from the engine, or those belts will be kissing the mounting bracket.
<<< So if moving the alternator away from the engine and installing longer belts worked (a little), I had an idea to continue that kind of thinking.  By adding some spacers, I could install even longer belts without the belts getting so close to the bracket. 

But then I had DOUBTS about the minor improvement I might gain with this idea
, so keep reading . . . .

<<< If I was going to the trouble of making a device to move the alternator away from the engine, making a bracket to add an IDLER PULLEY (back-side idler) would not be too far of a stretch.  The idea is to significantly increase belt wrap around that alternator pulley. 

A back-side idler is NOT normally done with a V-belt setup. Some people will tell you you shouldn't try it.  The main concern seems to be the potential for accelerated belt wear.  Well I already have that with a slipping alternator pulley. Plus so far all of these concerns appear to be based on opinion, not actual experience. 
So you can consider this to be EXPERIMENTAL.

Found this info later, so I thought I would add it here: 
Kevlar / Aramid belts are created to be stronger than standard v-belts. In a Kevlar belt, the normal polyester cords are replaced with the much stronger Kevlar cords. When using machinery with a back side idler, the belt takes a beating and normal belts can wear out faster. Kevlar drive belts are made to last longer in these situations.

Observations and Reasoning: 
There wasn't initially enough room between the crank pulley and alternator for an idler pulley unless the alternator was moved over first. 

A bracket that could also serve as a mount for the upper adjuster bracket would eliminate the need for a new longer custom upper adjuster bracket.

After a careful look, I could see there was actually room in a 240 to move the alternator over a couple inches.  Nothing seemed to interfere.

This has been suggested.
So let's pause for a minute and I'll explain
why I didn't move toward a SERPENTINE BELT SYSTEM.

I've see a number of people do variations of serpentine systems in Volvos, but so far I have not seen anyone do it for a Volvo with  alternator, water pump, power steering and AC using Volvo RED BLOCK accessories or with a PROPER TENSIONER PULLEY.
Sure, you can cobble together some pulley parts from other cars and adapt them, but you will still need a custom crank pulley (or custom B230 crank dampener).  And you will have to make all of the needed bracketry to hold all those idler pulleys.  In the end, will you get a better belt-wrap on the alternator than I can with my crazy idea?

This has also been suggested:
"Why don't I just give up and change to a 740/940 style alternator mounting?"
There's nothing really wrong with changing your 240 to the 740/940 style alternator mount. You just need the parts.  It requires new mounting brackets, maybe a new 740/940 style power steering pump and new or modified power steering hoses.  The only question I have is about potential belt slip.  Yes, this arrangement offers more belt-wrap on the alternator pulley, but it allows only ONE belt. Would that one belt be enough for my high output alternator?

<<< So I began playing with a bracket design to hold the idler pulley.  I started with making a prototype out of cardboard (not pictured).  Then I transferred that info to plastic to make the pictured model.  This is PVC plastic I bought from McMaster Carr.  It's easy to cut or grind and can be bent with some heat.  This material made it easy to make adjustments as I tested fitment over and over and over.

<<< For those who don't have a 240 close by to look at, here's the STOCK alternator pulley belt wrap situation. Of course the alternator pulley slips.  Why wouldn't it?

<<< Here's the plastic prototype bracket mounted on an engine with an idler pulley and alternator.  Making the bracket out of plastic gave me some flexibility when I found adjustments needed to be made. Moving the alternator a couple of inches away from the engine does not seem to be a problem in a 240. There's plenty of room in my 242. And the nice side-effect is there's more room for the oil pressure sender.
<<< I wanted this bracket to be able to use the stock adjuster bracket if needed, so I added this mounting ear for that.
<<< Then I had a working prototype made using 1/4 inch steel plate.

And I bought some steel spacers. These are 1.5 inches long and 7/8 inch in diameter. PN 4GVD9 from Grainger.com.

<<< Test-fitting the new steel prototype bracket.
You may have noticed. I changed pulleys.  There's more info below on this change.
<<< A view of the back-side and mounting ear for the adjuster bracket.
<<< This is the first idler pulley shown in the above pics.  I chose it mainly because I wanted to use a flat pulley with side flanges.  It was not expensive. I had some concerns about the durability of a pulley that was originally intended for a lawn tractor.  I could not find any specs other than what I have listed here, so I have no real reason for having reservations.  So after thinking it over, I concluded it would be more prudent to choose an idler that was actually designed for automotive use at auto engine speeds, etc. 
<<< So then I ordered one of these automotive pulleys.  I found it listed in the Dayco Pulley Guide (PDF below). 

Dayco offers only a good variety of pulleys, but relatively few are FLAT with side flanges with enough WIDTH for TWO v-belts.  The majority of the pulleys they offer are grooved pulleys (made for serpentine belt systems). All pulleys considered for this project have sealed ball bearing centers. Some in the catalog have 10 mm center holes and some have 17 mm center holes (and a few other sizes).

Also I noticed the majority of the pulleys listed had ONE center bearing, but a few had DUAL BEARINGS. An automotive grade pulley with a single bearing would probably be fine for this project, but I decided since something with two bearing was available, I would to try the dual bearing pulley shown here.  

We'll see if the grooves on this pulley present any issues with the back-sides of v-belts.

Dayco Pulley Guide: http://www.daycoproducts.com/stuff/contentmgr/files/17/f63f2a9acd46a2fa5140ade7b2423f73/files/dimensional_pulley_guide.pdf

<<< After testing the above configuration for about 600 miles with no negative issues, I decided to make an adjustment.  I raised the idler pulley up about two inches in order to increase belt-wrap around the alternator pulley.  As you can see in this pic, there is now more than 180 degrees of belt-wrap. Testing will now be done on this configuration.

After installing this in my 240, I tested the slip resistance by putting socket wrenches on the crank bolt and on the alternator pulley nut and applying torque.  This test before with the stock setup demonstrated a lot of slip on the alternator pulley.  Testing with this configuration showed that the alternator pulley now actually has slightly MORE GRIP than the crank pulley.
<<< Installed in my car for long-term road testing.
The only effect found that has been caused by the grooves is found in this photo.  The grooves etched lines onto the backs of the belts.  This began to appear after only a few miles and after hundreds of miles it has never changed
or increased.
<<< I don't think the lines above made by the grooves will be a problem, but if it becomes unwanted, a switch to this type of belt should eliminate it.  This is a Dayco Top-Cog belt.  It comes as a Top-Cog with a normal bottom 'V' in 0.44 inch or wider.  This 0.44 inch width does the 240 10 mm pulley just fine.
This special belt is also available as a "Gold Label" Top-Cog, which also has a bottom cog design, but this style is only available in 0.53 inch or wider.  This belt would be too wide for a 240 10 mm pulley.

More to follow . . .

davebarton.com prancingmoose.com 240turbo.com Contact Us
Shopping Cart
New Items Cool Volvo Products Volvo Stickers Steering Wheel Labels Prancing Moose Stickers
Body/Chassis Labels
Other Car Stickers
Volvo Wire Harnesses
Harness Parts/Connectors
Coil Repair Harnesses
Volvo Relays
240 Window Scrapers
740/940 Scrapers
740 Turbo/Boost Faces
Volvo Gauge Faces
Adj Voltage Regulators
Horn Buttons
740 Odometer Repair
850 Odometer Repair
240 Odometer Repair
240 Hydraulic Clutch
Classic Auto Air AC 4 Speed Fan Controller Limited Slip Read Ends 240 Mods and Fixes
Group A Racing
Electric Fan Diagrams
Tropical Fan Clutches
Modified 240 Favorites
Side Marker Lights
SoCal Salvage Yards
Unleaded Racing Fuel
B26FT Stroker
245 Spec Page
Vacuum Diagrams
Used Stuff
240 Big Brakes
R-Sport Apparel
Prancing Moose Apparel
Favorite Links
Ordering Instructions Policies Payments Shipping Returns
Volvo Meet Photos Texas Volvo Meets and Events Mojave Road Page 240 Door Vinyl 240 Alternator Mod Page
Online Payments