When you don't have heat you still have air coming out of he vent right?
I'm gonna assume you do:
Make sure you get all the air out of the cooling system, and your level of coolant is good.
Your heater core could be plugged. Install a flush kit and flush your heater core. One way to check is by touching the two heater hoses with car running at normal temp and heat set on high; they should both be very hot. If one is cold or luke warm, clean your heater core.
Also your blend door could be defective or the actuator broken.
Another thing I can think of is a weak water pump.
Finally, if your car has a heater control valve, make sure it's not 'sticky'.
I don't think replacing the temp sending unit would change anything.
Monday, November 17th, 2008 AT 6:38 PM