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  1. #1

    Default Electrical/Alternator issue on 1997 GMC Suburban

    On my 1997 GMC Suburban K1500 I noticed an interesting problem this morning. I started the truck and the battery light came on. The battery voltage gauge read approx 10V. It was clear the alternator was not charging the battery. I turned it off and then started it again with the same result. I then got out my DMM and checked voltage on the battery. It read about 11.4V again indicating no charge from alternator.

    So I started driving to my local auto parts store. About half way there, the alternator started charging the battery again (I saw the battery voltage gauge jump up to it's regular 14V). Of course the auto parts store electrical test equipment indicated everything was normal.

    So here's a bit of other background:
    Replaced the alternator in Dec 2009
    Replaced battery terminal leads approx Oct 2010

    My first thought is a bad connection somewhere (possibly a bad ground). Anyone have any ideas? What is the best way to start tracking down bad connection problems? Is there a chance it really could be the alternator?

    Thanks!
    1997 GMC Suburban K1500 5.7 L V8

  2. #2

    Default

    Still have side post battery? If so, double check the terminals are as tight as you can make them. If loose at all (with a little force), they are too loose and can cause your issue. It's pretty common, which is why I changed mine to top post battery to eliminate that issue.

  3. #3

    Default

    Yeah, I actually had that issue last year and went to great pains to replace the connectors. It is still sidepost (should have converted to top post) but yes, the connections are tight and appear to be making good connection (this was the first thing I checked).

  4. #4

    Default

    Assuming the battery is in good shape (load test if unsure), and belt is in good shape...I would not rule out the possibility of an intermittent alternator problem. Yes, it is possible. Have seen it a few times. The charging system is not really rocket science, so I would just make sure all connections associated with it are good. If so, take it to an AutoZone, or similar, for a test on the vehicle again, but have them run it several times just to see what happens. Sometimes the voltage regulator is affected by heat and can intermittently fail. Would be worth that effort to double check before tossing that $ to it. If test comes back failed even once, it's probably worth changing it out before it causes battery failure too.

  5. #5

    Default

    For anyone who is interested, it turned out that indeed the alternator was bad.

    All connections were good, but the alternator wasn't giving anything. I took it to the local auto parts store and they tested it to confirm my diagnosis. $120, and one hour later and I had a running truck.

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