AC defrost all the time

[deadbeat]

I am having a little trouble with the 1997 k1500 air, it only blows defrost no matter what setting you have, and nothing comes out any other vents. I changed the hear control panel with a known good used one out of dads truck, it did nothing. I have checked the fuses but it seems there is no power to the actuators, the one by the drivers pedal never moves. I really don't know where to start checking anymore and I don't like throwing parts at things and guessing. What should I check now?

 

[MIHELA]

Common problem. The Defroster doors warp and the seals rot off of them with age. It requires taking off the dash to get at. https://www.gmpartsdirect.com/oem-parts/gm-air-distributor-upper-case-52467204

 

[deadbeat]

I don't think this is the same problem, when that happens it will come out other vents too and you can hear and see the actuators move. I put a new defroster door on it a few years ago when it did that.

 

[deadbeat]

Looking at the diagram, I guess I need to verify power on the brown wire.

 

[deadbeat]

I think if I could find how to check the wires coming into the controls and where they come from I might be able to figure this out.

 

[deadbeat]

Ok, brown wire has power down to actuator, how do I check the actuator itself?

 

[deadbeat]

Changed the mode door blend motor, now it is working correct. I guess, if you air is stuck on either floor, defrost, or vent, this is where to start. I had power to it and I could move the levers easy with the motor off, the motor was locked up in the actuator.

 

[1998_K1500_Sub]

Glad to hear you found a fix... a relatively easy fix at that.