2001 Silverado - headlights dim when not accelerating?

[Faze3]

I noticed this morning when backing into a slot in the parking garage that if I let off the gas, the headlights dim. When I give it some gas, they noticably brighten.

Don't believe I've ever experienced this with any other vehicle.

It's a 4.8L with under 25K miles. First Chevy I've ever owned. Normal, or is this indicative of something serious?

[Nigel215]

i donno about that one. I know with my truck that if the heads are on or the high beams and i roll down the windown or use the power locks, they dim a bit until i let off the button. But that sort of makes sense. I donno how hitting the gas would make them brighter. maybe someone with a bit more understanding on this topic can answer that one for you.

[jeep_cj4x4]

The only thing I can think of is your alternator isnt putting out enough juice. It is but it's not. As the engines rev, the alt puts out more juice causing the lights to brighten. I'd have the alternator checked because you dont drive at idle and if it's not putting out enough, you may eventually drain the battery. Just a thought......

[jeverett]

You could go to a service station and have the alt. checked. Even the battery being weak will do this b/c most of the headlight load is placed on the battery, the alt is just keeping it from dying, so if the battery is weak.. makes sense doesn't it??

[jumpingjack66]

I would start pulling,checking ,and cleanig all battery cable connections first. Do this on the battery and starter and frame. These trucks have the remote battery connections for jumping and powering other devises so you have more connections to check then older cars..JJ

[broughy84]

Check all connections first, Battery +, Battery -, ground on frame, connections on alternator. Check and clean the corrosion off these. Then if it is still doing this let it idle with the headlights on and check the voltage at the battery with an voltmeter. It should be about 13-14V. If not take it to autozone, they can test it for free and let you know if it is a bad alternater or a bad battery.

[ponchonutty]

There is a TSB about bad power cables. Something about the batteries crack where you connect the cables then acid runs down inside the cables and eats them all up. I had mine replaced. Actually, I am on my 4th battery from the dealer and my truck is only a '01 with 40k miles on it.

[skipr]

If it turns out your battery is bad, invest in a gel cell battery, last longer, no liquid in it and they tend to hold up better in heat. Big problem with lead acid batteries is the heat frm being under the hood kills them within 5 years (the average life expectancy).

[Faze3]

Originally Posted by ponchonutty

There is a TSB about bad power cables. Something about the batteries crack where you connect the cables then acid runs down inside the cables and eats them all up. I had mine replaced. Actually, I am on my 4th battery from the dealer and my truck is only a '01 with 40k miles on it.

I imagine this is the problem. When I replaced the wiper tank pump, I noticed the battery appeared to have a small leak.

What's the TSB? And do you have to be the original owner/under warranty to be eligible for it? The battery's a ACDelco, which I assume to be the original.

..and its a 2001 with 25k.

[ponchonutty]

I don't remember the tsb on this. I am not sure they would cover it now under warranty anyway.

[Puffnstuff]

It should still fall under the 36k/3 year bumper to bumper warranty. Both of my last 2 new gm cars had to have the batteries replaced. If for some reason your truck is out of warranty then consider an optima red top battery.

[TexasF355F1]

I think this is just another annoying, yet liveable Chevy problem. Noticed this since the day I got my truck. Had new battery and other things since and the problem is still there.

Hey Chevy! Fix your fucking shit and quite it with the annoying little problems.

[Faze3]

Originally Posted by TexasF355F1

I think this is just another annoying, yet liveable Chevy problem. Noticed this since the day I got my truck. Had new battery and other things since and the problem is still there.

Regardless, I'm going to borrow a volt meter and make sure the alternator and battery are ok.

Thanks for everyone's input.

[Faze3]

Ok, so while driving into work this morning I happened to look down while at a light. Noticed the alternator gauge on the dash had dropped from 13 to about 11.

Every other time I checked it, I was coasting while in traffic rather than actually using the gas.

So does this mean battery or alternator? I've still to check it with the voltage meter.

Thanks guys!

[Puffnstuff]

Low volts means you need a new alternator since the regulator is in it.