I took off all of the hvac ducting and went through all of the hvac choices to watch the action of the blending doors. They all are functional. However, the middle door, controlled by the heater/ac actuator with 2 ports, moves in exactly the opposite way that it should given the hvac selection. When choosing ac, the door closes off the passage to ac ducting, opening the passage to heat ducting. Hence, ac comes out the heater openings. When choosing heat or defrost the middle door opens to ac ducting, closing off heat passage. Hence, heat would come out ac vents and no defrost. The defrost actuator, with one port, operates correctly given hvac choices.
I have found only one decent vacuum diagram. It is for a 1982 K25 with ac. It shows the blue and tan vacuum hoses on the heater/ac actuator switched between the 2 ports from the way I installed them.
So, does it look like I need to switch those 2 hoses to get the middle blending door to work correctly with hvac choice?
Thanks for your help.
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Friday, August 1st, 2025 AT 3:37 PM