Fresh air actuator

[Donald Mitchell]

OK, here's a good one. 1990 c1500 heat ac control with buttons. Which mode/button controls the fresh air actuator behind the blower. Trying to get the gears indexed. I know, I should have taken a photo but I didn't. The actuator works but I need to be sure its opening and closing the door properly. Thanks for any info.

 

[delta_p]

The wiring manual says turn on the a/c to max cold, fan to med or hi and 30 secs after the air inlet pressure switch closes (on the ac compressor) the motor will move the door to the recirc position. Says the door will move to the fresh air position 5 mins after the air inlet pressure switch opens, or immediately opens if the temp setting is raised, the blower set to LO, or the mode is set to floor vents.

page 68 '90 wiring manual
https://www.gmt400.com/threads/88-95-service-manuals.43575/

 

[Donald Mitchell]

Thanks, That helps me understand what it's doing.

 

[delta_p]

What does that air inlet pressure switch operate off of. Is it detecting the blower is on by pressure? I don't have one of those on my '96.

 

[Donald Mitchell]

I don't know, I have everything out of the truck. Installed new heater core and evaporator and cleaned everything. I hooked up the fresh air actuator on the lower part of the case just to see how it worked and it went to the closed position. So until I can get the air working it probably won't open. I'tll be fine!