Did some searching but didn't really see anything that was the same as my problem or question. So here it is.
My 98 Jimmy has the Auto Computer Climate controls. Seems the only thing that works is the heat. No matter where it is set only hot air blows out. It can be swapped from defrost to dash to floor. but its always heat. And the fan only blows wide open, nothing less.
I was wondering if I can change this control out for just a normal one, or has anyone else experienced this and can offer some advice on a fix.

Thanks Vandy

 

So is the blower always on the highest speed along with the temperature always on the hottest?

If it was only temperature I'd suggest that the blend-door actuator was bad but if you have both, it could be that the sensor that detects the interior temperature is bad or had become disconnected and now the climate control system reads this open circuit as the interior as always cold.

I'm speculating as I am not familiar with the failure mechanisms. However, assuming you have two parts of your system mis-behaving simultaneously, it would seem that the issue is with the control circuitry: the control electronics or the sensor that is connected to the control electronics.

As for putting an a manual control system, each system uses a different vacuum hose harness with different connectors to the control box.