Possible Electrical issue with Climate control?

[Shawn S]

Hi
I finally broke down and started replacing parts in the climate control to pin point the source of this issue. I don't think its the blend doors (Possible denial to avoid full dash removal in middle of winter) but i'm starting to think electrical but not sure where to start. I have a 2003 Ram 2500 with 5.7. So here we go.

This all started back in March in 2020 when it was chilly and had tried to use my defrosters and turned the system on an every thing seemed fine. Went down the road a few miles then on its own it changed to forward vents. I switched it back and was fine. Turned truck off and went into store. When I got back to truck and started it up vents were working fine then they switched on their own again to forward. Only this time they wouldn't switch back. Got home and a played with it a bit to discover that the floor stopped working as well. Decided I would try and old trick my old SAAB need once in awhile and hit the top of the dash. Sure enough in worked. Not a peep for about a week. Started doing same thing again. This time dash hit did nothing. I ignored the issue due to life and didn't have time to get to it.

Now brings us up to December 2020. Starting a week ago I got around to testing and replacing parts to see if I can get this defroster and floor working again. All fuses appear to be good. So I decided to replace the climate control unit itself with a new unit. After that was replaced everything worked for about 2 days then stopped again. I then went and put a new actuator in it (I turned the part it plugs into to see if the door there works and it moves door fine). Same thing again it started working fine then quit again.

So as it sits only things that don't work are the floor and defrost setting. My temp works fine (Minnesota winter cold and Sahara desert hot), A/c button works, mirror defrost works, and the fan speeds all work.

Is there anything electrical that could cause this or some kinda computer that needs to be programed. It seems odd to me if it were the doors because wouldn't they just break instead of working periodically? Anything else work me checking? Thanks in advance for any help.

 

[Oliver Closehauf]

Nod to a fellow SAAB guy. Below from the shop manual, looks like there is a calibration procedure. I don't see a way to do it like you can in an old SAAB by pushing a few buttons at the same time. Might need to -cough- go to a dealer.

OPERATION
The defrost door actuator is connected to the heater-
A/C control module through the vehicle electrical
system by a dedicated two-wire lead and connector
from the HVAC wire harness. The defrost door actuator
can move the defrost door in two directions.
When the heater-A/C control module pulls the voltage
on one side of the motor connection high and the
other connection low, the defrost door will move in
one direction. When the module reverses the polarity
of the voltage to the motor, the defrost door moves in
the opposite direction. When the module makes the
voltage to both connections high or both connections
low, the defrost door stops and will not move. These
same motor connections also provide a feedback signal
to the heater-A/C control module. This feedback
signal allows the module to monitor the operation
and relative positions of the defrost door actuator
and the defrost door. The heater-A/C control module
learns the defrost door stop positions during the calibration
procedure and will store a Diagnostic Trouble
Code (DTC) for any problems it detects in the
defrost door actuator circuits. The defrost door actuator
can be diagnosed using a DRBIIIt scan tool.
Refer to Body Diagnostic Procedures.