Question about 2002 GMC Yukon XL

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Is there a switch or relay that kicks on/off the alternator on on a 2002 GMC Yukon XL? Problem: Battery drains while driving (or just warming up) and engine dies. Occurs only after startup on cold mornings. At startup, voltmeter gauge does not jump to 14+ as normal and gradually drops until engine dies - as if alternator not kicking in. Reving engine has no effect. I recharge battery, start engine, and things work fine (voltmeter immediately goes to 14+ and stays there) and can drive all day. The next 'cold' morning at startup, voltmeter again fails to jump to 14+ and gradually drops until engine dies. Does not occur on warm days. Alternator was replaced but problem continues. Battery cables checked with amp/ohm meters - good.

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  • gmorganiii Jan 31, 2010

    2002 Yukon XL Alternator switch question: Shouldn't be a battery issue since: 1. Battery tests ok and holds its charge for an extentended period when at rest. 2. The battery does holds its charge at times (as long as the voltmeter gauge on the indtrument panel reads 14+). 3. Wnen the battery does drain, its only after a cold-weather engine start and the voltmeter gauge fails to jump to 14+ (and hold constatn) right after the engine starts running. Instead, the gauge gradually drops (battery draining) and engine dies after a few minutes.

  • gmorganiii Feb 06, 2010

    Update to Yukon 2002 alternator issue: Over the past week, when I start the engine, the voltmeter initially jumps to 10 then gradually drops to less than 9 over a matter of minutes. But just before the engine dies, you can hear the altenator kick in and the voltmeter jumps to 14, then promptly drops to 9 then jumps back to 14 and then stays there for the duration. Next morning, this repeats itself.

    Is there a low-voltage sensor or some other sensor that could be abnormally kicking in and out due to the cold morning temps? If so, do I need to replace this sensor?



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You need a new alternator my friend and because you have been running it only on the battery,i would also get a new battery.if you can still start it you will notice that the low battery light comes on.

Posted on Nov 09, 2012

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Sounds like the battery has a dead cell in it. i would get a new battery.

Posted on Jan 31, 2010


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