Update:
I made it home Sunday with no further problems.
Discovered the high speed quit working on my fan motor.
I am almost 100% certain that the fan speed resistor is the culprit.
Had this happen about 8 or so years ago. Driving, suddenly the cab filled up with smoke. Thought it was on fire, I hit the shoulder, nailed the brakes and actually bailed and ran a safe distance away. Wasn't on fire, so I started it up and drove away. Fan resistor had shorted out and melted the wire terminal block, causing the smoke and smell.
Same smell, I recognize it.
My theory is it shorted out just before shutting the thing off. Sitting overnight, it somehow drained the batteries. Not sure but I think the power to the resistor block is hot at all times.
Haven't got in there yet to check it, but will this weekend.
I think GM had a TSB on this issue some time ago.
