If it blows air (but air is not hot), it could be the heater core, a heater control valve, weak water pump, defective blend door, defective actuator, bad thermostat (is your car taking a long time to warm up?).
Check your heater core inlet and outlet hoses. If they're both hot, your heater core is probably okay, as well as your heater control valve (it doesn't mean that your water pump is good though).
If the inlet hose is hot up to the valve and cold after the valve, your valve is stuck closed and you need to replace it.
To check your blend door and actuator, you're gonna have to remove the glove box.
The actuator is the white box on top of your heater box.
First, turn the control to COLD (full blast) for a few seconds. Now turn off the car. Disconnect the harness hooked to the actuator, and pry the actuator loose. Now plug the harness back, and turn over the actuator. You'll see the part that moves the blend door (it goes to the heater).
Okay turn your key to ON and turn temp control to full hot this time. If the actuator is working good, you should see the part that goes to the blend door making a quarter of a turn (about 90 degrees). If it doesn't move, your actuator is bad (make sure your actuator is getting power though). Now if it moves, your actuator is okay, but you probably have a broken blend door.
Before you put the actuator back, make sure you put the temp control back to full cold, otherwise the actuator won't go back in place.
If it doesn't blow air at all, you should check your blower motor.
Wednesday, October 22nd, 2008 AT 9:04 AM