Currently my AC unit gives out either only very cold air or else heat. Like it's either on maximum heat or max cooling, no in between. I can adjust the digital temp control, but it doesn't have any effect, until around 84 degrees. At 85 the heat kicks on, go to 84 and it's full AC.

Is there a likely sensor causing this? Anyone had to fix this issue before?

 

The auto climate control system has 4 or 5 temperature sensors. Run the self diagnostic to see what kind of results you will get.

You didn't say what year your car is. It is very important for some kinds of problems.

Here is a link to the self diagnostic procedure for a 2001 Maxima. I think it will work on all years. It starts on page 37.

http://boredmder.com/FSMs/Nissan/Maxima/2001/HA.pdf

There is a sunlight sensor in the system. If you have the car in the garage, it will probably fail that test.

 

Thanks for the link! I'll try that. The car is a 2000.