Delayed Charging... Battery? Alternator? Voltage Regulator?
 

Hello all,

Having a problem with my car. Delayed alternator charging, gen light turning on during cold start up. Battery discharging, etc. Today i was playing with the OBD menus, and noticed while the gen light was on, i was around 11 and change volts, and after some light driving and warm up, the alternator jumps to 13.5-14.2 Are the brushes in the regulator bad? It almost seems as if they're sticking on cold startup after sitting for a while... Anyone suffer from any similar experience? Lmk your thoughts, all input is appreciated.

If its taking more than 10 seconds to start fully charging after cranking its probably on its way out (alternator).

I dont think the alternator is bad. It charges at normal voltage after a light warm up. I can drive the car for 50 miles straight with no problems, its in the morning that causes problems. Alternators should easily last 100k plus. Thus leading me to believe it is the regulator. Unless of course the oem valeo alternator is that s*&$ that it goes out after 65k...

I refurbished mine for $20 for kit that included brushes and slip rings. Very satisfying project !

I think that when crowz says alternator on its way out he is including the VR as part of the whole since most people won't replace part of a part.



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I’m at 100k and had to replace the alternator twice on the 3.0i...

Yeah I figured thats what he meant but why spend 500 when the regulator is 50 bucks at fcp... what were your symptoms?

Symptoms?? 2 times in 100k sounds ridiculous :sorry:

First time simply the battery light came on while driving. Got towed to a mechanic....alternator replaced. Second time was 2 years ago...turned on the car in the morning... a hell of a noise similar to when the power steering pump sucks air. No battery light...until I revedup to 3.000rpm...then you could see the battery light coming on. That time i replaced the alternator by myself... It's a straight forward job in the end - speaking of a 3.0i!

Speaking in defense of those alternators...the ATF reservoir that is positioned above them tends to leak from the hose connections and the drops go straight on the alternator. It's not a lot, but probably a drop here and then is not helping the alternator to expand it's lifetime. It's just a guess...

With your symptoms, it is not easy to nail it down 100% to the alternator. Still I would go for it...mostly if you are thinking of keeping the car a few more years. It will come in handy anyways sooner or later....

I never said replace it. I said the alternator is on the way out.

That's the same thing as telling you the knocking noise your engine is making means the motor is on the way out. I could of said its the $3 rod bearing.

Still looking at a motor rebuild.

The voltage regulator is getting lazy kicking in the alternator since we want to get technical.

This could be caused by brushes, the regulator or a few gallons of power steering fluid aka atf fluid. I have fixed them with any and all of the three causes.

Its still the alternator croaking.


If it is the atf fluid make sure to clean it out completely if you decide to rebuild. It will greatly shorten the life of the new parts and randomly cause it to cut out or not charge from time to time.

Is there any DIY information available on the rebuilding process? I would like to give it a try next time...

Yep. There are several of them out there including youtube vids.

This is a good one for bosch alternators for example.

DIY: 1998 528i Bosch Alternator Rebuild for $30! - Bimmerfest - BMW Forums

Thanks a lot....well, I guess i threw 800 bucks down the toilet over the last couple of years by thinking a alternator was a very sofisticated part that couldn't be serviced. Should have done more research on this...

Search my name I posted pics of my rebuild with I believe a link to the YouTube video I used for reference and several tips that make it much easier (such as using heat to release the potting epoxy vs chisel out cold and a much easier way to remove the old slip rings).


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Don't feel bad on that part. I have rebuilt a bunch of them over the years and I normally just buy a reman or new alternator.

Its not worth the effort in the matter to me. On a bmw unless you have a parts washer they get so nasty on the inside of the alternator from the power steering leaking into them combined with road grime I would rather just replace it than rebuild it. But to each their own.

The ones I will redo brush and regulator wise are the ones that can be done without removing the alternator. My F150 and the Mercedes 190D Turbo can be redone without removing the alternator itself. That's worth the effort for sure.

But with the trouble it takes to get to the bmw's alternator plus how nasty it gets I just replace it.

Two screws hold the regulator/brushes to the alternator after you remove the plastic cover. If you can't get the screw out with a regular screwdriver I would suggest you get one of those handheld impact with a phillip bit to remove the screw. If you mess up that screw then, and the only way to remove it is to drill it out.

Delayed Charging... Battery? Alternator? Voltage Regulator?
 

Mine failed from oil when my oil filter o-ring failed. The alternator was an oily disaster but a pump sprayer with Dawn detergent and a scrub brush did wonders.