2005 gmc 1500 alternator problems?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=83154
Printed Date: May 13, 2025 at 6:33 PM
Topic: 2005 gmc 1500 alternator problems?
Posted By: ryguy
Subject: 2005 gmc 1500 alternator problems?
Date Posted: September 20, 2006 at 6:27 PM
any one have any problems with stock alternator. shutting down and not charging ? then coming back after a while but not at full out put . replaced alt. does the same thing ? figuring that he volage regulator is over loading any way to fix this ?? any ideas ?
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MECP installer,technician
Replies:
Posted By: haemphyst
Date Posted: September 20, 2006 at 11:22 PM
The regulator is internal on that truch, and I think it is probably controlled by the ECU, as are so many accessories today. I'd take it to the dealer for a diagnosis of the ECU, but that's just me...
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: Mad Scientists
Date Posted: September 21, 2006 at 11:16 AM
I know that GM does control the alternator through the PCM on some models; I've seen it. I can't say for certain about your truck though. Can you describe what you're seeing that allows you to say that it's shutting down, then charging, but not at full rate? Are you measuring volts or amps? A good indie shop should be able to help you with this.. it might be something to consider if you have extensive aftermarket electronics installed; dealers can get wierd when something comes in with a problem and they see aftrmarket stuff installed. If the dealer doesn't like what they see they can have your warranty voided on that system (in this case, electrical), as well as just claim it's the aftermarket stuff without truly determining if it is or not. Jim
Posted By: ryguy
Date Posted: September 21, 2006 at 4:29 PM
what is happening is there is no out put from the altenator . the gauge on he dash drops right down to 0 . there is a huge stereo in theis truck . this truck has 2 altenators one big one for the stereo and one for the truck . the one for the truck shuts down . i was thinking the voltge regulator was over heating or overloading but i have heard there is some sort of power save feature in ther new gm pick ups but not sure how to fix or by pass this problem . thank you for your responses
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MECP installer,technician
Posted By: geepherder
Date Posted: September 21, 2006 at 9:53 PM
Verify alternator output with a meter at the alternator, not the battery. Measure dc voltage with the positive lead on the big lug with the fat wire from the battery and the negative lead on the casing of the alternator. If the voltage is constant, you probably have an intermittent connection somewhere. Ensure the battery cables are clean/tight. Also, see if the alternator lead is fused. On my old Honda, I had a hair line crack through a fusible link which caused the car to die. I read 10 volts at the battery, and 16 at the alt.
If the voltage at the alternator also jumps around, I'd suggest having the pcm checked as recommended above.
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My ex once told me I have a perfect face for radio.
Posted By: Mad Scientists
Date Posted: September 22, 2006 at 8:43 AM
Are the two charging systems interconnected?.. Is the stereo alternator a factory install? (doesn't sound like it). I'd try going to a local independent shop and having them look at the PCM data (WRT alternator charging) with a scan tool before I went to a dealer.. as most of us can attest to, if you show up at a dealer with all that aftermarket stuff they'll most likely claim that's the problem. While it may indeed be the problem, it might not be.. and they aren't going to be interested in finding that out. Jim
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