Alternator

2011 GMC SIERRA
52,500 MILES • 4.8L • 2WD
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CWEED
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  • 1 POST
Driving on the highway for about fifteen to twenty minutes, with the A/C on my charging gauge goes down to about 12. Fifteen minutes later it goes back up to 14.6. Up and down for ten hours of driving. No problem starting back up and the gauge where it is suppose to be. Without the A/C on, it does not do this. People told me a bad regulator and some said a belt slipping. three people have looked at the belt, it looks good. Battery and alternator are original.
Jun 28, 2017 at 4:25 PM
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WRENCHTECH
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  • 20,761 POSTS
You have an automatic tension-er on a multi-rib belt so the belt is not slipping. The regulator is incorporated into the alternator. It sounds like the alternator is failing. Change it now before it ruins your battery.
Jun 28, 2017 at 5:00 PM