Oldsmobile/Buick Repair: inside heater, buick roadmaster, air cond

Question
Hi Billy, i have a Buick Roadmaster 1991 and when i put the haeter on ex 65f it blows either verry hot or verry cold at all time, so the temerature in the car is not stedy on 65 it is going up and down drasic!
So what can i do?

Best regards

Chris in cold Sweden

Answer
hi chris..lol yes the notorious dntrol.well here is the prob,your car is designed to incorporate the air cond and heater to for a blend air mix.the thermostat is malfuntioning.it can be repaired but very expensive and difficult to do.your other option unplug the air comp you don,t need it makeing it colder .good luck please take a moment of your time to rate my help ty billymac