HVAC does not blow hot

[Scheitan]

Hi,
after changing the HVAC Controller in my 1996 Suburban (as the connections of the original one were disintegrating) I cannot seem to get hot air anymore. Looking at the movement of the blend door actuator, it seems that it only goes from cold / open to half, not all the way to hot / closed.
As this is certainly less than convenient for Finnish winters, I was wondering if there might be a way to calibrate the limits, or if I need to see about yet another replacement control unit.
All the best.

 

[1998_K1500_Sub]

In 1998 and I believe 1996 the blend door actuator responds to voltage signal from a potentiometer in the control module.

See attached, from the 1998 FSM, and look for the "TEMP DIAL" on the figure.

IMHO, the voltage on that LT BLU wire from the control module to the actuator should range linearly from ~0V to ~12V as you move the temp control knob through its range of motion.

If the voltage on LT BLU doesn't doesn't reach the extremes of ~0V and ~12V, the actuator won't move through its full range.

You should be able to test the actuator by connecting it's LT BLU input to GND and +12; it should move to its limits of motion.

This is my understanding of the operation. I've not actually measured this myself on my Suburban.

@east302 is the guy I think of when think about HVAC air handler operation and control.

 

[Scheitan]

Thank you! I'll have a look at that and will report back

 

[Scheitan]

So I checked (my apologies for the late reply) and it seems the output is between 0 and 7V instead of going up to 12.
So it makes sense that the actuator does not go through the full range of travel

 

[Scheitan]

I suppose that means I bought the wrong panel, or is that a matter of settings somehow on the panel?

 

[east302]

If you still have your original panel, I’d put it back in and compare. But yes, I’d suspect that the panel is defective if the wiring connector is sound.

 

[Scheitan]

I have the original Panel still (though last time I put it back, it seemed completely dead). The heat settings used to work before though.
I wouldn't put my hands in the fire for the soundlness of the wiring...every single connector on that car seems to sporadically lose the will to work

 

[Cadillacmak]

Greetings from Alaska, and from a Makinen. My great grandparents came from Finland.