I have a lxi concord which blows the same temp (hot) even when i turn the dial to lo 60 degrees, on the heat mode and even on the ac mode.. The compressor is kicking on but still blows the same temp about 112 degrees.. The one ac line is cold and the other side is hot.. My wifes sister gave me the car and they had the evap replaced along with the climate controls assembly, but that was a used unit..They said it did work but that was in December and they never tried it after that.. I was thinking it could be that used control panel in the dash or the a/c blend door actuator.. Like i said even in heat mode the temp won't change when i turn the dial from 90 degrees to 60 degrees, then i turn a/c on and no real change in temp, maybe 4 gegrees but the compressor is on.. thank you for any reply!!!

 

I realize this is old, but if you're reading this and having the same problem w/ your ATC (Automatic Temperature Control) it could be the Internal Temperature Sensor located in the dash.