Alternator problems?

[Erick]

Hey guys,

back on e3s I posted about a problem with unstable RPMs, that the idling of the car was rough with the RPMs jumping from 500-800rpm when I'm stopped.

I just noticed 1 thing though that made me think it could be the alternator instead of the ECU, however this is just a guess.

What happens in the car is that whenever I turn the headlights on ( or sometimes when the engine is cold ) the RPMs are unstable..... when I turn off the headlights the RPMs level out at 600 and they stay like that.

1 thing I also noticed is that with the headlights on, whenever the RPMs reach it's peak at it's unstable idling, the headlights become really bright, and when the RPMs drop they lose some of that brightness.... so it keeps getting brighter and darker as the RPMs jump around.

Talking to my father about that, he started saying that it could be the alternator. What do you guys think?

Thanks,
Erick

[randomtask37]

my guess would also be the alternator

[AndrewBird]

I would also agree. Just go to a local electrical repair shop and have them test it for ya. That is the easiest way to find out.

Andrew

[E30_Dave]

Just to throw something else in, you don't say what model your car is. If your engine is a stock 4 cylinder, I'd say 600rpm is a little low - I'd expect around 800rpm. It may be that your ECU is sensing low idle speed, and momentarily opening the idle valve.

Does you car have aircon ?

Cheers

Dave.

[NC325iC]

this thread was 11 years old when you joined r3v...

[MrBurgundy]

just to throw something else in, you don't say what model your car is. If your engine is a stock 4 cylinder, i'd say 600rpm is a little low - i'd expect around 800rpm. It may be that your ecu is sensing low idle speed, and momentarily opening the idle valve.

Does you car have aircon ?

Cheers

dave.

this thread is 13 years old, brooooooo. You're crazy, Dave, and I like it.

[PKile]

This thread is as old as my wife's E46....

[E30_Dave]

Sorry guys - It was still near the top of the stack!... Do we think he found a cure ?

[TobyB]

Wow. That's kinda awesome.

t