Thread: heater problems/no heat

lately i have been trying to use the heater in my car. and it only works on the defrost mode but just barly. i have no clue whaat it could be. it just warm air, and also on all the modes like feet or heat or even defrost it only comes out the passanger side and on the driver side its cold air. ive checked the inlet and outlet hoses and the're just nuke warm. not hot. any advice would be amazing. its freezing and i need the heat really bad. thanks guys.

but the car runs at opperating temp

My passenger side heat doesn't work on my '02 GTP. I found it was my heater control unit. I haven't replaced it yet ($260 for part), so for the enterim I have taken out the motorized controller and turn the vent control shaft to the heat position for winter. The passenger side is located behind the glove box and towards the lower center. Two screws hold the controller in, then disconnect an electrical connector. I haven't had to do the drivers side, it still works. While troubleshooting this I noticed that the controller would operate if I pushed the temp controller to the right as I raised it to the heat position. This tells me that the wiper on the potentiometer is not making good contact (broken). I have dealer shop manuals and can look up how to access the drivers side if you need. It's a pain not to have full control of the passenger side, but for now it will do. So the quick troubleshoot may be to put side pressure on the temp control while raising it to hot and see if the air temp changes. If this doesn't change the temperature it doesn't prove the temp control unit isn't bad though. Manually turning the vent shaft will prove the controller or temp control unit is bad. A new controller is $60 at the dealer. I bought one as the first part of my troubleshooting. Hind-sight is 20/20.
You could take the drivers side out and install it to the connector of the passenger side then turn ignition on and watch the plastic driver on the back of the controller to see if it rotates. Total rotation is about 60 degrees, so start at cold and raise to hot while watching. Ensure the passenger side controller works while watching it also before testing the drivers side controller. You can e-mail me at tjljmcoyle@juno.com for a faster responce. I don't frequent the forum that often. Good luck and enjoy the challenge of troubleshooting if you can. I'll help as much as I can.
TMC Tim