batteries go dead, 07.5 2500HD, deisel

Discussion in 'GM Electrical Tech' started by henrys021500hd, Mar 8, 2012.

  1. henrys021500hd

    henrys021500hd Rockstar

    I have had this issue off and on for almost a year. I park the truck, 07.5 deisel and then a day or so later the batteries are near/ or dead. Two new batteries last fall and it did the same in late Oct while at the dealers so they cleaned and tightened pass side battery cable. We went on a trip and put on 11,000 Kilometers with no trouble. Moved the truck Sat and then Mon batteries dead again. I charged them and started the truck. Battery gauge showed just over 9V and did not start to climb for a good min to 2. When I had it in in the fall I asked about the gauge readings and was told it was normal, I have never seen a volt gauge low just after starting. I wonder if the alt is going and causing a discharge through it. I am now 4000Kl out of warantee. My buddy sugested that I remove both battery +s and connect a light between the main + post and the main cable to the starter and see if there is a drain from something, and if so start removing fuses. Before I go through this any ideas? Also does anyone have a reference as to which fused circuits should be live without the key on? Thanks and good day.
  2. The only thing that I have seen that causes that problem is the alternator is junk. I would see what it is putting out while running with no load on it, and then with a load (a/c, lights, radio, etc) if the meter drops significantly then the alternator is junk.
  3. sstoner911

    sstoner911 Epic Member 5+ Years 1000 Posts

    It could be the alternator... I would have it tested. A friend of mine had a nissan maxima that would sometimes do as you described. It would be fine for a month then the battery would be dead every morning. He replaced the alternator, battery, and cables. He even had the electrical system gone through. Never did figure it out..he ended up selling it.

    Chances are he had something remaining on that would drain the battery...your friend has a good idea with the light. I dread electrical issues in the newer cars and trucks...make me cringe.

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