I have a 2003 Honda Civic Hybrid with the temperature control dial that can be set anywhere between ~62F-80F. For the last two years it has worked well and always been a comfortable ride.

Something is busted. Today the car gets way too warm regardless of heat setting. It seems to spew out hot air unless I crank it all the way down to 62F (the last click), where it finally turns off the heater all together and very cold air will come through.

My guess is some kind of thermometer/sensor is faulty. Can someone point me to the possible part number and a guide or instructions (or a book) for replacement?

 

An extremely rare possibility is for the vent stepper motors to get stuck in the heater position.