I have a 2000 Chevy Blazer. I'm having problems with control of the temperature with the ac/heater. The fan blows fine to areas selected but the heat/cool temp does not adjust. I either have all hot, or all cold air depending on if I have the heater or a/c on.
The answer someone gave me (which worked) is:
I have seen this problem with these vehicles before. This system is very dependent on an input from an in-car temperature sensor. This sensor is mounted to the roof under the headliner, just above the driver front door opening.What you will have to do is remove the trim panels from around the door opening and lower the headliner to gain access to the sensor.
The system will regulate the temperature inside the car to what you set it to dependent on the sensor readings. If the sensor is giving the control module a false input that it is too hot in the vehicle then the only way to get heat is to turn the system to full hot (which is a default that ignores the sensor).
I would replace the sensor and this should correct the concern.
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