Auto Air Conditioning & Heater Repair: heating problems in my trailblazer, chevy trailblazer, climate control system

Question
I have a 2000 Chevy Trailblazer and the heat doesn't work in it. We have replaced the thermostat twice so that is working properly. We have also flushed the heater core. Both hoses coming from the heater core are hot like they are supposed to be and the heater core isnt leaking at all, but still when you turn the heat on all that blows out of the vents is freezing cold air. What else could cause this to happen?

Answer
Hello
For one reason or another the flaps are not moving to allow the heat off the matrix.
If it is a full climate control system they are likely to be contolled electronically
Typically thist type of system will have an LCD readout on the control panel.

If you have traditional red & blue controls, the flaps may be controlled by rods or vacuum.
What you need to know is are the moving.
Start the engine, select the second fan speed then turn the air direction selector on the heater.
You should be able to hear the flaps move, if not, let me know and if you need more help I will find out more information