Do you have anything on the display for the temp control unit?
Sometimes the display on mine will dissapear, and then the blower will come on at a present speed, sort of slow, and the temp will be quite hot. I didn't know what was going on so I started pressing buttons to no avail. Then I smacked the side of the dashboard, right next to it, and the display came back on and worked like it should. It did it again and smacking it didn't help, so I kept pressing buttons and it eventually came back on. This last time it did it it wouldn't come on at all, and it was cold. I went to the grocery store, and when I came back out to go home it worked like nothing was wrong. Who knows?
If you can get to actually having the unit work right, try this, it's the ATC head diagnostic.
1. Make sure car is running, can't be moving though.
2. Make sure temperature is set at 75 degrees.
3. Press and hold the floor, mix and defrost buttons at the same time. They are all in the top row, the first, second and last button. When done the display will blink.
If there are any error codes they will be displayed where the temperature normally is. Press the panel button to see if there is more than one code.
Here is the codes and descriptions. Unfortunately, I have no idea how to fix these stupid things.
Code Description
23 ATC Blend Door Feedback Failure
24 ATC Mode Door Feedback Failure
25 Ambient Sensor
26 ATC In-Car Sensor
27 Sun Sensor Failure
31 ATC Recirculation Door Stall Failure
32 ATC Blend Door Stall Failure
33 ATC Mode Door Stall Failure
34 Engine Temperature Message not Received
35 Evaporator Sensor Failure
36 ATC Head Communication Failure
When I do this to my car, I get a code 36. But I don't have a manual that I can use to actually try and fix this. I figure if it gets bad enough, it's in the ATC head itself, and I have a spare on hand that I can put in. Most of the time the stupid thing works though, so I don't worry about it. If it stopped, like yours are doing, I would be confused.
Good Luck!!
Dan