Heater not working, why?

The heater on my 1997 Lumina does not heat up. The AC works very well. Could the control nob switch be broken, is there a fuse that could be blown, is there an elecrical motor that opens the heater valve or could the car just run to cool to heat it up? I welcome all replies. Thank you.:banghead:

You could be low on engine coolant or you could have a stuck thermostat. Did you just recently flush your cooling system?

Coolant up to levels, thermostat appears to open as the temp guage registers fluctuations in temperature. Just purchased vehicle and cooling system is clean. Thanks for the reply.:)

vacuum line controlling the air door?

thought about this afterwards... maybe you have the same problem with the dexcool causing corrosion and sludge deposits in your cooling system... perhaps the heater core occasionally has blockages due to sludge? You say your coolant is clear now... but was it recently replaced?

or maybe you need to purge the air out of your radiator? there are two bleeders on your engine.