TLDR: Blazer wouldn't start two nights in a row after driving. First time the security light was illuminated solid, second time the vehicle had no electrical power. Much more detail below.

So I have my theories as to what's going on, but I don't want to divulge and lead people astray, so I'll just outline the symptoms. Vehicle is a 2005 4.3 Vortech 4x4 Blazer.

Blazer wouldn't start last night when my wife drove into town and described symptoms of a dead battery so I went down there to give her a jump. Brought the cables and a multimeter.

When I arrived the key was locked in the ignition and wouldn't come out. I checked the battery voltage and it read about 12.5. Connected my car anyway and checked battery voltage again and it read about 14.

The key would not come out of the ignition with my car hooked up. Tried to fire up the truck and it turned over and fired but then immediately died. We called the tow truck but me being the tinkerer I didn't want to wait around idle.

Tried a few more jump starts before finally locking the Blazer, except the key fob lock button didn't lock the truck, it opened the rear hatch. None of the other buttons did anything. I checked the dash and noticed the Security light was staying illuminated whether the key was in the ignition or not.

Checked the fuses, in particular the Passlock fuse, and it was fine. Reinstalled the fuse and wiggled it, pressed firmly to ensure it was fully seated, then checked the dash. The security light was off. Cranked the Blazer over and it fired up and ran like nothing was wrong. Headed home for the night.

Fast forward to today and we went to get gas and the Blazer again didn't start except this time it had no electrical response (as if the battery was totally dead) and the key stuck in the ignition again. I tested battery voltage and it was again 12.5 or so and tried the fuse thing once more, it didn't work. I started to disconnect the battery and as I was doing so, my wife yells that the truck has power. I tighten the battery bolt back down and turn the truck on and it fires up with no issue.

Any troubleshooting suggestions? Like I said, I may have an idea as to what's going on, but I'm hoping for someone more knowledgeable to chime in without me putting any incorrect guesses in their head. As a disclaimer, I have not yet done any troubleshooting other than visual inspection of wiring which seems fine.

 

I saw that no one had yet replied so I thought I'd take a stab at this.

I have heard of others having trouble with the ignition switch. My closest experience was when while driving my 82 Honda Prelude died because of the ignition switch. It was dead as a door-nail. Good thing it happened when I was going slow in small town. Bad thing was I was 25 miles from home and had to get a friend to come get me.

For our Blazers, from what I've seen in the forums, there can be lots of weird electrical symptoms that go with an ignition switch that is acting up and on it way out but not quite completely broken.

You might try searching for related threads to see if any of them give you guidance.

Good Luck!