The fan works, blows air, does the different speeds, but the temperature cannot be adjusted. No hot air from heater, no cold air from ac. The coolant looks full. What can I try myself before taking it to a mechanic?
My car has 111000 miles.
My car has a manual transmission.
It sounds like the blend door may be stuck. The blend door is usually controlled by a cable or an actuator. If the switch itself seems to be hard to turn, it is likely cable driven and experiencing a restriction.
If this is the case, I would recommend having the cable inspected for damages. If the switch will move easily but no temperature adjustment occurs, the blend door is likely driven by an electronic actuator. If this is the case, I would recommend having the actuator tested for proper function.
If the actuator or cable has failed, you’ll need to have them replaced as soon as possible in order to resolve this issue. I recommend having a certified technician, such as one from YourMechanic, inspect the system to determine why the heating and AC are not working.