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240 Alternator Page

     UPDATED: July 13, 2019                       CONTACT       
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What to Do with Your Old 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, 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 more 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 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, unlike the above large Bosch.
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:

Here's a YouTube video on removing/replacing a Volvo 240 alternator: https://www.youtube.com/watch?v=A72pWPYm8yo

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 style housing that has been set up to correctly fit in the factory Volvo mounting location (while using a few spacers).

<<< 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 to 10 x 950 mm
I swung the new Mechman slightly further from the engine and the
new belt size used was 10 x 965 or 10 x 975 mm.
<<< The above 10 x 975 mm belt size is pretty much the maximum size that you can use.  Swinging the alternator further from the engine could result in the belt contacting the alternator mount just above this long bolt head.
<<< Attaching a ground was a bit different.  This Mechman alternator did not 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. Using a good lock-nut on that long bolt is a must.

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.   

<<< 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 this 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.  It has been known to break that bolt in the block for the adjusting bracket and a few people have broken their water pump pulleys. It can prematurely wear out your water pump and generally your belts don't last as long as they should. They wear faster and then begin slipping again sooner.


Update 2019:
Got a New Bigger/Better Mechman
<<< I got a new one.  It's actually physically 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 a hairpin stator type.
I wish someone had educated ME about hairpin stators BEFORE I BOUGHT THAT LAST MECHMAN!
The below photo will show you how different a hairpin stator looks (left photo) compared to a normal stator (right photo).

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

Here's some more info from Mechman below about this alternator.


Here's the dyno specs for my new 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 14.8-14.9 volts (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 AT 14.7 volts! Even at IDLE!

So what if I wait until the alternator gets SUPER HOT?  Remember that 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 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?  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 . . .   Dealing with that Belt Slip
I began a discussion thread on this project: http://forums.turbobricks.com/showthread.php?t=350085

SYMPTOMS: 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 grip.  This was an immediate problem when running my AC (along with my big Lincoln Mark VIII fan and dual condenser 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 that 10 x 925 and 10 x 950 mm were prone to slipping way too easily.  I thought I had a solution until the new belts would no longer grip after a few thousand miles of use.  Plus 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 gauge drop from 14.7 to the mid to low 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 any more room to swing the alternator any further from the engine than this, or those belts will be kissing the 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 too close to the bracket. 

But then I had doubts about the minor improvement I might gain
, so keep reading . . . .

So the above pic might have helped a little, but instead I decided to try a different direction.

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

This is NOT something that's normally done with a V-belt setup.  So you can consider this to be EXPERIMENTAL.

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.

More to follow . . .

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