01 Suburban Lights Dimming (Different than post below)

[JBP]

Hi folks - I'm a new guy who just purchased an 01 Suburban 2500 4wd with 49K miles. Very nice truck! However, I am experiencing an intermittent electrical problem.

In stop-and-go traffic, I noticed that when letting off the throttle, the lights will dim significantly. This seems to be a function of engine rpm, and it is accompanied by the voltmeter lowering from approximately 16-17V down to 14V or a bit lower. The lights will then brighten back up and the voltage raise as if nothing happened. I checked the battery when I got home and the battery temperature seemed fine. I tend to think that it is an alternator/voltage regulator problem...but I'm no expert on Suburbans!

Could anyone please advise on this problem and how to solve it? Is it an annoyance to live with for now or does it need to get fixed ASAP? Any advice is appreciated.

Thanks much,
Jon

[jfmctlaw]

All alternator/generator output is a function of engine rpms. The faster the alt/gen spins, the more voltage/current it will generate. When rpms begin to fall below 900/1000 the output performance really falls off quickly. You don't say what your rpms are falling to. It could be that your engine idle is too low. This is why when you jump start another car, you raise the rpms on the engine to about 1500 because it brings the voltage up and thus the current being provided to the dead battery. Your Sub is also old enough to where the battery is a possible suspect, but if you're starting fine, it's probably ok.

[JBP]

Thanks much for the input - this seems to occur around 1200 to 1500 rpms when the motor is heading back down towards idle after letting off the throttle.

What rpm should my motor idle at? I have the 6.0L.

The vehicle starts fine, and it is getting pretty cold here - so I think the battery's okay.

Could it be a headlight relay problem? Though I haven't tried extensively, it has not seemed to occur with the lights off.

Thanks,
Jon

[bkaschak]

I have the exact same problem on a 2001 2500 4x4 so your problem is not isolated. If anyone has a suggestion please advise. I am going to the dealer monday to have it checked out.

[theffv]

Have a 2001 1500 4x4 with flickering dash and headlights that would occur in idle and disappear when running but also noticed dash and headlamps were dimming over time. Problem was getting worse and the truck wouldn't start on two seperate isolated instances. Idle didn't seem to be where it should be.

Performed the "transmission" workaround listed on this message board but it didn't solve the problem.

Then, it was diagnosed with a bad battery which was changed but didn't solve the problem.

A dealer wanted $450 just for a new altenator before labor!
Had another dealer install a new altenator for $250 - Problem Solved!

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*B E S T*
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TheFFV