It's been an issue for several months. Last Nov. I got a new battery because the Hummer was dead. About April it was dead again. I charged it a couple times but after a week or so of sitting it would be dead. So Advanced Auto gave me another new battery this past spring. All seemed well but I also had been using it weekly. Recently I took the windshield cowel off the get painted and have not used the Hummer for a couple of weeks. So today I went out to get the IPass out of the windshield for a trip to Chicago tomorrow and the battery was dead. Key did open the door this time and I made the mistake of trying to start it even though everything was dead. I've been through this too many times this past year to be that dumb. The key won't come out of the ignition when the battery is dead. Not wanting to leave it in there while I'm gone I get out the battery charger. Hook it up and the needle was not dancing around like it usually does. Nothing for an hour. I was going to jump start it and my neighbor brought over his portable battery starter. I hooked it up and turned it on and the security horn started blaring. I remembered it doing that in the past and thought it would take a minute or so to stop. It did. There was the usual clicking sound coming from the engine compartment/ dash area. That stopped after about 5 minutes. I figured as the battery gets charged this stuff stops. It was enough power to let the key loose from the ignition. So I was going to just leave it at that and deal with it next week. I hooked up the battery charger and let it sit. About 4 hours. It got up to about 6 amps. Tried to start the Hummer and it would just die right away. Four times. So not wanting to kill the battery more I decided to call it a day. I was putting away the charger and it was dark. The radio (aftermarket) was still on when I looked at the truck. I could not turn it off but it's a digital Pioneer that always has lights on when the truck is on, I think.
Nothing else. No interior lights, no lock working...nothing. so I figured I should pull the radio fuse. Hey, maybe I just never noticed in a year that the radio was not going off. I just don't know. So I get the manual out of the glove box and that light was working. I made sure it would go out when I closed it and it did. Pulled the fuse from under the hood. I turn around and the interior lights are on. The door locks function. The Hummer started up normally. So I guess I will let it run tomorrow for a couple of hours and charge up the battery without the radio and see what happens after a week or so. I hope the drain is this easy. I was reading about different causes and I can't think or many changes I've done that would start the drain. The trailer wire connection cap got knocked off so I figured maybe moisture would be making a connection and causing an issue. A few years ago I went with the springs in the rear but don't know if the bags were disconnected fully. I feel like I've heard the compressor fire up since then. Maybe that's the drain. The drivers seat heater coming on and going off by itself. Maybe that's the draw. So many possibilities and I'm not adept at the work to figure it out so it's gonna be costly. Anyone have any insight why everything started working after I pulled a 15amp radio fuse?

 

what hummer is it..

 

It's an 04 H2. Ive had it 11 years. When I said air bags I meant to say for the suspension.

 

It's an 04 H2. Ive had it 11 years. When I said air bags I meant to say for the suspension.

 

it sounds like you are having 2 separate power related issues? one being bad connections to the battery or bad grounds and the other being the power drain?

 

MOVED for you to the H2 section where all H2 tech questions belong.

I assume you used an adapter to install the aftermarket head unit? If so what model/brand? Some have a history of the module going bad/shorting and it could be like leaving the radio on all the time........ which over time can drain the battery.

 

No idea. Battery cables are fine. Look new. When the battery is drained everything acts funky as it's coming back up on charge. Then it's all normal when the battery is charged.

 

Use the search feature for parasitic. There have been a number of pretty in depth threads over the years on here of others tracking things down on this.

One common thing is removing the VCIM fuse in the underhood fuse box. That is for the old non-functional 3G Onstar module. With that fuse in the Onstar system is always looking for a 3G cellular signal which is no longer available.

 

Yeah, it's pretty overwhelming reading about all 5je possibilities and work involved lol

 

bronxteck is referring to chassis grounds. Old vehicles need all attention to all of them as connections deteriorate with time, not to mention road grime/salt corrosion.

I am going with the radio adapter interface. A clue is what happens when you pull the radio fuse. Let's see where it goes.

Best of luck.