Alternator???

[Matty]

I have a 1985 318i and as of late it has been acting wierd. While I am driving the tach will suddenly begin to act possessed and jump around like crazy and it sounds like the engine runs a little rough, but not horribly so. If i floor it the tach catches and its ok for a while. If I dont see it and let it go, the stereo goes dead and possibly the headlights, but I dont remember. If the stereo and fan and everything are turned off it is less likely to do it. My only guess is the alternator or some sort of voltage regulator or something like that. Does this sound familiar to anyone??

[DIRTE30]

Sounds like your voltage regulator is going funny. Pretty tell tale symptoms. You can probably buy this piece at your local parts house for not too much. It is located within the alternator, pretty straight foreward installation. Should be an easy fix!

[yammahamma]

I replaced my alternator for $150...that includes a new regulator....I felt better replacing the whole thing, because it could be the regulator among other things....so i'd hate to replace it one peice at a time only costing me more in the end then a new alternator would cost....

but I guess that depends how much a regulator costs...

[JoeMadoo]

You could just take it to autozone and have them test it and the voltage regulator. An alternator either works or it dosent, its just a hunk of copper. A regulator is like 20 bucks.

[Matty]

Well I just got her back from the shop and they said it was the battery indicator light. It was burned out and making intermittent connection. This is necessary to complete the circuit so what happened was that the alternator stopped charging and the computer was dying. They replaced the bulb and tested everything and now everything is fine. Hopefully someone else can use this information and not spend $100 to have a bulb replaced. But I never would have guessed that was it so it’s ok. Well I just got her back from the shop and they said it was the battery indicator light. It was burned out and making intermittent connection. This is necessary to complete the circuit so what happened was that the alternator stopped charging and the computer was dying. They replaced the bulb and tested everything and now everything is fine. Hopefully someone else can use this information and not spend $100 to have a bulb replaced. But I never would have guessed that was it so it’s ok.