A/C in reverse

I have a 2000 DTS. A/C works fine when outside temperature is mid 80 and below. Above mid 80 and 90 degrees outside A/C blows hot air through all vents. Any ideas? Thanks Guys. 

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ORIGINAL: derrickwi

I have a 2000 DTS. A/C works fine when outside temperature is mid 80 and below. Above mid 80 and 90 degrees outside A/C blows hot air through all vents. Any ideas? Thanks Guys. 

sounds like a sensor is shutting system down.
low refrig?
engine running to hot?

 Thanks. Engine doesnt read hot.
 
Even at moderate temps left side is blowing a little warmer than right. Swapped over   temp sensors left and right. No difference. I am beginning to think its the instrument panel module. I get a code B0429 but thats the rear hvac door actuator. Again manual points to IPM. I think thats a dealer replacement isnt it because the manual says it has to be calibrated 
 
Thanks again.

Alsos checked refrig. Thats OK