Electrical problems in 98 M3

[Kissner]

Hey everyong, long time since I been on here but I'm hoping your help will respark my interest in online forums. My 98 M3's battery light came on the other day, followed a few days later by my headlights going out, windows not working, interior lights going out and eventually my tach and speedo going out. After throwing jumper cables on it and letting it charge for 10 minutes or so I got a good 2 miles before all the same things happened again. Am I looking at a bad battery or alternator? Or something else? Battery was replaced a year ago and has not been run dry yet, so I would thnk that wouldnt be it. Any help is greatly appreciated. Thanks

[CanadianWraith]

have your alternator tested, sounds like it's done

[Kissner]

any way to test it myself or do u mean a shop? I"m trying to avoid a shop because of lack of money. I have a college buddy with an M and he has a shop I can do the work at, I just wanted to make sure it was the alternator before i ordered it and put the work in. Any other options or way to confirm it's the alternator?

[witeshark]

Some auto parts stores will do a free electrical check.

[drz]

Remove teh alternator and take it to an auto parts stre. Have them bench test it for you. Do keep in mind that if the problem is with teh voltage regulator, which is embedded in the alternator for these cars, it may very well still pass the bench test.

[Kissner]

Can i figure out he problem without the shop? I found a buddy whose parents happen to own a shop 20 miles from here, so I'm gonna drive it their and work on it. Does anyone know the brand or anything of the factory alternator, so I can make sure I'm buying the right replacement?

[drz]

Yes, you can figure out the problem without a shop. But first, take the alternator to the auto parts store for them to bench test the alternator for free.

As far as the brand, you will have to remove it to see if you have the Bosch unit or the Valeo unit. I would replace with the same thing I took off.

[Kissner]

Why not upgrade to 120 amp? I have HID high and low beams and a fairly large stereo, it seems like getting a larger one would make more sense. If I mess with a different amperature alternator will i have to worry about fitment? The site says it's a direct replacement for OEM

[drz]

It should be okay.

[318kid]

not an electric genious as i have my own electric problems but you should probably put a capacitor or two if you have a big system.

[Kissner]

My car has the Valeo unit. Can someone tell me if any of these are the correct one?
Discount Car Parts Stuff - Car Accessories & Truck Accessories - Cheap Auto Parts - Car Cover - Floor Mats - Cargo Liner - 1998 BMW M3 Alternator Stock Replacement
Please look at the higher amp ones, 80 or 140

[drz]

Looks like the right one. Is this a seller you know and trust?