For a comfortable drive through all four seasons, the Chevrolet Trailblazer A/C heater control is there for you. However, if either, or both, of the heating and cooling functions aren't working, you might seriously suffer in extreme weather conditions during the summer or winter. Which is why before this happens to you, be wary of any signs that your A/C heater control might be faulty. To know what to look out for, learn how to check for any problems with these tips.
When either function--heating or cooling--is not working, the blend door actuator in the affected side might be bad or stuck. To check, take off the plastic cover under the dashboard, close the affected side's door, and lean in on the floor from the other side. Afterwards, put the truck in "accessory" and then move the climate control for one side--fully COOL first then fully WARM--at a time. Whenever you switch to another function, listen closely for the sound of the electric motor spinning in the actuator to know if the heater and cooler work. If you don't hear a sound, then there might be a problem with the wiring connector.
If you don't want to look under the dash, you can also check the actuator in another way. After letting the engine reach its normal operating temperature, adjust the A/C unit to fully COOL function and check for cool air discharge in all areas. Then, do the same for fully WARM function and check for warm air. Then slightly vary the controls from fully WARM all the way to fully COOL while checking for temperature changes. If you don't feel any temperature change--e.g. the cool air discharge doesn't get warm or the other way around--then check the A/C unit's fuse.
Another possible cause of a malfunctioning A/C heater control could be a blown fuse. To find the A/C unit's fuse, open the Trailblazer's driver's side door and use a flathead screwdriver to remove the cover from the fuse panel. Look for the fuse labeled "HVAC 1." If you see it blown or broken, then take the faulty component out and replace it with a new one.
If the fuse is fine, then the culprit could be the wiring connector. To find it, remove the four screws from the dashboard bezel that's covering the radio and A/C unit controls, then take the bezel out. Inside, you'll find the A/C unit. Remove the two screws securing it and pull the unit out slowly. Behind it is the wiring connector. To check if it's malfunctioning, gently tug on the cable--if it comes loose, secure it to the A/C unit. However, if this doesn't work, you may have to replace the unit itself.