ok whats the culprit in the digital heat a/c systems in 1988 C1500 trucks that causes the infamnous motor running engaging noise behind the control panel middle of dash with key ign turned on and then off?

unplug or disable or replace or what? where at exactly?

Not sure I understand the issue, can you try again, and maybe add some punctuation?

Sounds like the an actuator. Do you get air flow through all the different positions? Defrost, floor etc.

I would 2nd an actuator issue. The plastic gears would "skip" at the end of actuator travel and keep running for a while then shut off. Find the one that is making the noise and replace it. not uncommon issue. hope this is helpful