I just got my maxima and the a/c blows cold one day and warm the next. I was driving on the highway today in OD, when I slowed down and the car downshifted to 3rd automatically, the a/c started blowing warm air. Is there some kind of vacuum switch that may be causing this? Thanks in advance.

 

yes... its supposed to do that... it interprets a down shift to high rpms as a need for power and disconnects the ac compressor so there is less drag on the motor..