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Doug, ASE Certified Technician
Category: Volvo
Satisfied Customers: 8604
Experience:  Volvo Enthusiast and extended work experience from a Volvo specialized shop
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Volvo S60: After I put in a new alternator (old one had bad

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After I put in a new alternator (old one had bad bearings) it would not start charging until the engine was revved to about 2500 rpm. Once it kicks in it stays on and charges even at idle. Shut off the car and you have to rev to 2500 rpm again to get it started. Advance gave me another one, it does the same thing. The way this car is driven, it may not get to 2500 rpm. There is 12 volts present at the small wire when the engine is running, even at idle. What did I do? Could it be that both new alternators are bad?

Unfortunately you will likely be dealing with two malfunctioning alternators.
Volvos do not get along well with aftermarket alternators at all; this is why Volvo and distributors are able to charge so much for genuine units, and also why used ones command such a high dollar as well.

There is nothing you would have done that could have caused the vehicle to develop this symptom. What is occurring is referred to as "exciting" the alternator, and only two things can cause this behavior: inherent design and internal failure. Some alternators are intended to operate this way (though generally more heavy duty units used in diesels that are started and idled long periods), but usually it is just a quality control issue.

Knowing the system was serviced due to a bearing problem and not the current problem, we know this issue is a direct result of the change of alternator.
The only things you could have done while replacing the unit would be short something to ground (if the battery was hooked up) which would blow a fuse would not cause a charging problem only under a certain speed then excited it operates. A short that blows a fuse would only result in zero operation until the fuse was replaced.

At this point your best bet here is to ditch the aftermarket alternator and get either a new/reman Volvo alternator or source a used alternator. With an 0 for 2 record so far, I would not invest any more time in trying more alternators that are likely to have compatibility issues as well. A genuine unit should resolve your issues.
Customer: replied 3 years ago.

I was afraid of that. I'll get a genuine unit and put in. May I contact you after the job is done (which will be a few days) to let you knw what happened?

Absolutely James, I am here every afternoon and evening, just please allow me some time to respond in case I am away or with a client when you post.

I'm sure you'll be fine; this is far from the first time I've seen this, and again all things being equal (no cable left loose or damaged etc) there isn't really anything you could do that could alter behavior yourself anyway... only cause it to not work at all.
Never the less, I'll be here. Let me know how you do.
Doug and 4 other Volvo Specialists are ready to help you
Customer: replied 3 years ago.

Doug, You were right. I put in a reman volvo and it came on and worked right away. Thanks for your help.




ps I also have problem with a 1987 Mercedes Diesel turbocharger that I would like to ask about. Can you recommend someone or should I just ask the question in the new question box?

Hey, fantastic James!

I know it sounds like hokum when you hear stuff like that ("Boo aftermarket, Yay Volvo!"), but sadly it is just the way it is. These companies make hundreds of different models of alternator and probably 100 other products as well to support just as many models.... they can't be bothered with a few complaints about their stuff not working on a single model within a brand that has maybe 4% market share? They don't care, all they see that is a very small percentage of the entire catalog of alternators (or whatever) they make failing and call it collateral damages for doing business.
See the same thing happen on a Camry or something that sell more units in a month than Volvo sells all year etc... then heads start rolling.

Anyway.... I'm glad it is all sorted out. Unfortunately I couldn't tell you a thing about an 87 Mercedes.... outside my specific field entirely.
I'm sure if you post a new question in the Mercedes category you'll get squared up shortly. I do not have anyone specific I could recommend however.

If I can do anything else for you just let me know, and have a great weekend James!