Like said, just bought it and going by what the seller said, since the issue isn't present at this time.
He did say that he put in a new battery and the alternator looks to be new as well which I think someone talked him into because of this problem.
Upon inspection, I saw that it had the heavy old style battery connectors and for looking brand new as well.
I'm thinking that he had this issue after this work was done as well, from the way he talked
Anyway, we'll see what happens as time goes on and go from there.

 

Easy test.... put a volt meter on the battery and see what the reading is at rest, should be 12.6+.

Let us know how it goes.

 

Better to test voltage at the bcm or any auxiliary port.

 

12.54 on a really old fluke and 12.6 exactly on a much newer digital clamp on.
But, like said, we haven't had the issue in the couple days that we've owned it and just today for getting a new title and the plates transferred.
This vehicle appears to be part of the seller's collection and or investment, since I'm seeing less than 1K miles on it in less than the year he owned it.
He said to drive it, and you should be fine, so taking it that he let it sit for long periods and for letting the battery go down.
Now, the one thing I've noticed from day one, is that it doesn't really crank over all that fast compared to most, so not sure if the starter's dragging bit or if that's normal on a GM Hummer.
I mean it starts OK, just cranks sort of slow.

 

I am not blowing off this task. I found a more important problem in that coolant is getting burned through the exhaust and maybe in the oil too.
So it may be a month or two before I get back to this one.

 

That's a real bummer for sure.
Do keep us posted of your findings, if you will.

 

Long story short: the truck is alive and well and I fixed the pesky driver door lock issue.

I was going to buy the electric actuator module like linked above. You have to choose between an aftermarket Chinese built one, and an OEM "refurbished" unit. The refurbished ones allow a core charge of $5. This got me thinking. What if I can refurbish mine? Well, that's what I did! I used a razor blade knife to cut it open.

Inside that actuator module is a small DC motor that looks like this:
"10mm Flat Shaft Central Door Lock Actuator Motor FC-280PC-22125 FLAT SHAFT, D Spindle, Power Locking Repair Engine"

Only the problem with that is, the original has a square piece covering the motor's pinion so it can connect to a worm gear. In the process of trying to get that off, I noticed something. The motor would spin fine out of the module (un-loaded), but once it went back in the motor would work less and less each time I applied 13V (yeap,13vdc benchtop). I popped off the backside of the motor. Within that plastic back cap is a Thermistor that is 1/4"x1/4" by a few mm thick. The motor was wanting to draw more current, but this inline inhibitor was preventing that (as current goes up, so does resistance and that reduces the voltage seen by the motor). So, I deleted it and replaced it with a small piece of aluminum. I also cleaned out the carbon build up. I used my soldering gun to melt the plastic seams of the module when I put it back together.

Works like a champ. crisp and clean locks and unlocks.

If some dummy leans on the lock button, and the motor blows up before the supply fuse blows, I may regret this approach. But I just love me some free fixes on 20+ year old vehicles.