[maxisp2000]

OK! I was trying to be brief. My failure mode is exactly the same as the OP. I have 177,000 mile on the engine.
1996 Chevy S10 Blazer 4x4 4.3 Vortec Vin Code W.
The air blend door actuator breaks because the door cycles each time power is removed and applied. Think of the carriage assy on a printer when you power up. Mine broke the main gear inside and was stuck with the heater full on.
Brand new fuel pump.
Cannot test anything when engine will not start.
It sets no codes. Every now and then I get evap codes, because of the gas cap.
No check engine lights for this problem.
Replacement parts are from Autozone usually.
Why would I open a new thread for the exact same problem?

The car runs fine when the ambient is less than 80 degrees. I went from Las Vegas to Phoenix and back last week when it was in the 60s.

I ran across a mechanic who said their kid had the same car, and it had the same problem. He said that they spent an entire day chasing wires under the dash to fix this problem. When I pulled the dash, I cleaned all the contacts I could find. I thought that would fix any wiring problems under the dash. I found two relays I did not take the time to identify. One was stuck on the HVAC covers and was wide and rectangular. Another was wrapped in foam and installed into the fascia. I think one is the HVAC high fan speed.

Also, I don't know if this is a hint, but my HVAC fan will stop running at the high speed setting when it gets warm too. This is a new fan, and fan speed regulator and control plate.
Another hint is opening the hood seems to cool off whatever is stopping the engine, so I think it's under the hood , not the dash wiring. That's why I thought it was the ICM to begin with. I replaced that last summer and drove from Las Vegas to Tucson and back in the heat of the summer. So I thought I had fixed it.
That's why I am thinking maybe the VCM or spider and injector.
I also know that I need to change my 4X4 vacuum switch, but that's unrelated.
An expert would help here.