heating not working on 1998 Oldsmobile Bravada

heat not working,blowing moter works it changes from one heater tpye to another by its self,from deforst to front vent blows out cold air not heat?

2 answers
I just replaced mine. I had to take the dash apart and on the passenger side by the heater core is a small switch that cost around $180. It sounds worse than what it is, you need to pull the dash up and back, just far enough to get in to it. It's held in by 3 screws and a plug located by the heater core. Tear apart/replace/and put back together was around 2hours. DON'T waste your $$$ on a new control panel like I did.
Check this out, it might help: http://repairpal.com/i-have-no-heat-what-could-be-wrong