Why are my lights dimming...

[carshateme]

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]

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]

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

 

[Frank Berry]

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

 

[AndrewT]

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]

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]

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]

I was talking engine speed.

 

[Frank Berry]

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

 

[carshateme]

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

 

[AndrewT]

Your light bulbs are dimming because they are not getting enough voltage.

no, the current demand is too high.

 

[Frank Berry]

... and that's why they are not getting enough voltage.
They are drawing more current than the system can supply. As a result, the voltage goes down.

 

[carshateme]

no, the current demand is too high.

If that was the case, they why wouldn't the light bulbs blow when I hit like 4,000 rpm

 

[Perry Babin]

Because the voltage is regulated.

 

[carshateme]

Ah I see. That's the regulator, isn't it?

 

[Frank Berry]

You might want to visit this website. It explains the automotive charging system:
Automotive Charging Systems -  A Short Course on How They Work

 

[carshateme]

Thank you. Was too lazy to research it on google =D

 

[carshateme]

The only reason I bought this up was because my wiring goes from battery>starter>alternator and not battery>alternator...so I just wanted to make sure I wasn't having a problem with the wiring. Although if that was the case.. I'm screwed because there is no way to bypass it.

 

[carshateme]

Well I just looked at my volt meter again..it's now sitting at 15 volts now...That's bad, isn't it?

 

[Perry Babin]

15v is a bit too high. Are you sure that the meter is accurate?

Put a digital multimeter across the battery terminals to see the true voltage.