I replace my AC compressor and dryer about 6 months ago. Full of refrigerant and no leaks. Worked just fine yesterday.Today I start the car and it blows nothing but HOT air. I can push it down to 65 degrees on the control panel and it doesn't respond at all. The last couple of months, I heard a small servo like motor randomly going on and off from what seems to be behind the clock or ac control panel area. Blower is operating fine. Engine temp is fine. Any ideas would be much appreciated.

 

I would guess that digital unit is going out? Do you hear the compressor enaging??

 

The first thing to do is see if the compressor is running. That answer will determine which way to go from there.

I would also suggest you run the self diagnostic on the AC control system. It starts on page 70 of the FSM.

FSM - http://www.nicoclub.com/FSM/Maxima/1997/HA.pdf

There are 3 motors under the dash associated with the climate control system.
1 - motor for inside air recirculation, located above the glove box.
2 - motor to move air diverters for air vent selection, located on right side of driver's foot well about ashtray height.
3 - motor for air temperature mix door, located just above the ECU.

 

Sounds like it could be the mixing door.

 

One more bit of information. When I try to select the defrost mode, it doesn't change the air blowing from the the front vents. Now its stuck on cold and Im freezing my butt off in the morning. Anyone have a link on how to remove the air blend Module or do you think it might be the AC control module on the dash?

 

Coupled with the a/c problem, it sounds like the control panel could be bad.

Why don't you run the self diagnostic on the system? The direction for the self diagnostic start on page 71 of section HA in the 1997 FSM.

Link to diagnostic - http://boredmder.com/FSMs/Nissan/Maxima/1997/HA.pdf

You could also run the manual operational check that starts on page 66.