T800 hvac controller, defrost inop

[joed2323]

2009 t800 daycab, hvac controller on the dash will not switch from front/floor vents to defroster.

I actually swapped the hvac controller out of another 2009 truck since they cost $777 and it worked, had full function of the defrost/vent .. Two weeks went by and now it's stuck and will not switch just like the first time I swapped it.

So tried swapping with a 2011, and it still is inop.

So im guessing their has to be something else the electronic controlled hvac controller communicates with to switch from vents to defroster. Does anyone know if their is a resistor or relay in the dash somewhere?

Looking at the fuse panel their is only a fuse hvac con, and hvac motor fuse, obviously these are good since the controller has power but will not switch to defrost, what am I missing or overlooking???

[Hammerhead]

They look like a Grand Piano, only Barbie doll sized. They get the command from the controller and have a servo that rotates the air deflector door to the selected position. A similar item is located under the hood where the hot water line comes into the heater core to control the temperature for an example of what your looking for. I haven't done one yet on my '09 T800, but on my '97 Pete it was behind the glove box and I'd assume it's probably in a similar spot on the KW based on heater core location.

[joed2323]

That's exactly what it is. Removed glove box. Banged on actuator with screwdriver, she started working again.

Have one ordered. Thank you sir

[Hammerhead]

No problem. Just payin it forward...
We've all been helped here by others, it's nice to be able to help back...

When you've got the actuator off, move the shaft back and forth to make sure it moves freely. If it's sticky I use silicone spray, dust doesn't accumulate on it as quickly as oil based lubes.