Hummer H3 parasitic battery drain?

I have a 2007 Hummer H3 (base model with towing package). The battery is dead each morning when I try to start it.


I'm able to successfully jump start it and I let it run for 30 minutes to charge the battery. I did a battery test at Auto Zone and they said the battery is good.


I suspected the alternator, but there is no voltage guage on the H3, so I just let the H3 run in my driveway for about 30 minutes (it never died).


If I leave it overnight, the battery is dead again! WTF? Also, the key fob suddenly doesn't unlock the doors anymore, even when the battery is charged.


:wall:


I've never had any electrical work done on the vehicle. None of my aftermarket mods are electrical. I haven't changed anything in over 2 years.


It seems that something is draining the battery and I don't know how to figure this out. I did a search and found others with similar problems, but I didn't find any actual solutions. Anybody have an idea where I should start in getting this fixed?

Still have the original battery terminals and cables?

Yes, but I have a 2007 model. I was under the impression that only the 2006 model had a problem with the battery terminals.

Check the wiring harness at the rear of the vehicle. I do a bunch of bumper swaps, and about 3 out of 10...have the wires rubbed through. Check the harness where it plugs onto the back of the trailer lighting socket, and in the nearby vicinity. There is a seam in the body, and the harness tends to lay against the seam and short out. It will be near the license plate along the front edge of the rear bumper (where it meets the body). They sometimes get burnt by the muffler too.

4speed is right on target. So, clarifying - no extra lights, radios, anything plugged into 12V accessory, radar detector, no aftermarket security system? As for terminals, at least early 07 models had crappy terminals too. They switched about the same time as the other mid-07 changes, like moving window switches forward.

FYI, my key fob does not work when I have a tablet plugged into the 12V accessory outlet. Unplug the tablet, fob works again.

Check the connections. A bad connection will still allow a trickle charge from the altenator to allow for a quick restart BUT after several hours the little charge you had is gone. No matter what, replace the factory connections, cheap and easy fix.

how old is the battery?

I had trouble with parasitic drain, and it really was a pull-ever-fuse-and-check to determine what the issue was (irony is the guy who I paid to do the fuse-pull was the cause of the drain - he reconnected a relay incorrectly)

that said, I had trouble also with a GTO (LS2) where the computer wouldn't shut off.