Your head unit is bad.

 

So what's the head unit and how do I get to it?

 

Something is not connected correctly. Or the ground wires are loose.
by control switch do you mean you replaced the hvac panel?

 

yes the switch panel in the dash. Whole new unit.

 

If you have a good scan tool you can see what it's doing. I assume you made sure the unit has good power and ground.
I really need to quite assuming things.

 

is there power to the motor?
is there continuity between the motor and the switch and resistor pack?
is there continuity between the resitor pack and ground?
does the AC compressor turn on when the switch is turned with the AC button on?
There is a splice in the orange wire near the motor that has been known to fail.

I don't know how a professional (expensive) scantool could possibly help. The only connection to the BCM is the "blower on" signal. I also don't know what the headunit might have to do with the blower

 

A head unit or HU is the radio, nothing to do with the HVAC control panel.

 

We tend to call the module the head unit regardless of the modules function. The head in this case is the HVAC module.

 

Tomato Tomatoe, I don’t Donbrew doesn’t, RJ doesn’t, just trying to keep any confusion down.

 

….Im wondering if ground path (wiring) is bad between your fan speed resistor and switch….or ground beyond the switch