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carshateme 30th October 2011 05:10 PM

Why are my lights dimming...
I don't know if it's usual...but just had a big 3 upgrade and such, everything is done right, the grounds are all stripped clean metal and mounted correctly...when my car is in idle, it dims, but when I rev the engine...everything is fine. Idk if it's because I have old light bulbs or what...

Perry Babin 30th October 2011 05:23 PM

The alternator isn't producing enough current at idle to keep up with demand. When the engine speed increases, the alternator can produce enough current to reach the regulated voltage.

carshateme 30th October 2011 05:30 PM

The alternator is a 220 amp though...I never noticed the difference with my stock alternator.

Frank Berry 30th October 2011 05:34 PM

It's 220 amps ..... but at what RPM?
Alternators don't put out maximum current when the engine is at idle speed.

AndrewT 30th October 2011 05:45 PM

your current demand exceeds your current capability.

BTW, old fashioned dynamos behaved like old fashioned labourers, They slogged away even at low revs to try to give the current output demanded.
Modern alternators are much like modern workers. They refuse to work hard unless you pay them well. They need revs. If you are interested in this difference look up the output vs revs plots for the two different styles of generators.

carshateme 30th October 2011 05:45 PM

Ah okay, I just didn't know if I needed to replace my light bulbs...because the light bulbs are like 13 years old. I think I get 200amps at 2.3 rpm or somewhere around there. Maybe 1.7rpm..I don't remember the specs on it. But I was just thinking that if it's a 220 amp alternator, it should be producing my amps.

AndrewT 30th October 2011 05:53 PM

That is very slow rotation, I think you mean 1700rpm.

But, is that alternator rpm or engine rpm?
The alternator drive will almost certainly turn the alternator at a different rotational speed from the engine.

carshateme 30th October 2011 05:56 PM

I was talking engine speed.

Frank Berry 30th October 2011 05:56 PM

Your light bulbs are dimming because they are not getting enough voltage.
Their age has nothing to do with it.

carshateme 30th October 2011 06:01 PM

But..umm my car is producing 14.4v, I already put a volt meter up to it.

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