Hello the car is a 1997 lexus sc300. The car was parked for a year. The ac wasn't working. I changed a 15a fuse and the ac turns on now. However the mode is stuck on max hot. When I press the modem switch nothing changes. Why is this and how do I fix

 

i would replace the AC temp plug/harness **** to adjust the temp (the one thats right above your radio volume) to see if that is functioning properly.

might need to unplug and reconnect so it reset the pins for new contact in case "the elements" cause a bad connection.

this will require you to take off the center console housing. not hard just takes time & gentle patience to not crack anything.

worse case is that you might need to replace the A/C unit it self. (might not be the issue since the unit turns on)

but i would start there and check to see if all the plugs are properly connected to the unit.

 

Lets hope it's not your blend door actuator etc.
This is what repairing mine looked like.

 

Aggreed the blend door actuator sucks but you can wesel it out without dissassembling the whole thing