Full heat or Max A/C only

[carpfisher]

Bought a '97 Explorer. 170K
The HVAC blows 100% heat or Max AC only. In reg A/C mode Only blows Hot full Heat. Temp knob doesn't affect temp.
Doors move and will blow DEF/Vent or Floor on demand. Fan control works.

Is this a HVAC Controller issue? Should I replace the control?

Thanks upfront for the responses

Greg

 

[Turdle]

Sounds more like the blend door is not functioning.

 

[carpfisher]

I was wondering about that also. I did a search on blend door and there are 80-gazillion blend door threads.
Can some direct me to the correct thread or provide a some guidance on on checking this out?