Hi
I recently inherited my grandfathers GS and I noticed that the passenger side doesn't work it only blows extremely hot air but the driver side and rear blow cool I was wondering if anyone else had this problem

 

This is pretty common. The actuator for the temperature control on the passenger side has malfunctioned/died. It's located up in the passenger side foot compartment. Up on the left side of the passenger foot well area. Kind of a pain to get a screwdriver on, because one of the heater pipes runs right in front of it as I recall, but it's doable.

 

Please google servo motors. You’ll find plenty of threads on this subject.