the accuator, located in the rear passenger side is bad. the controls in front when turned go to an accuator in the rear there are two of them one for hot/cold and one for the vents.
if it doesn't heat your heater core is most likely clogged and if it doesn't blow at all then the blower is messed up.
Heater core may be defective
Could be low on coolant.
The temp blend door actuator is broken.
The heater core of a 2004 Chevy Tahoe is used to provide a source of heat to the cabin. When the heater is turned on, air is blown across the heater core which is constantly supplied with hot coolant from the engine.
Have you checked your suction lines.
Do both heated seats turn off, or just one?, do they start to heat?, if they cut out right away, there could be a short in the heating element in the seat, causing the c/b to cut out, resulting in the switch re-setting(off).
You can take a blow dryer and heat it up, real hot. It might come loose. Most of the time you have to brake it up in piecess to get it out.
Check the blower fuse located in the hood. It's a 40 amp fuse. Marked blower on the map
heat/ac actuator
my 94 explorer wont blow heat
An air conditioner blows out heat