Q: Heater is not working - 2003 Chevrolet S10

Hello. A malfunctioning heater can be caused by many things. The first thing I would do is check to make sure that the coolant is topped off at the proper level. If it is low, coolant may not be reaching the heater core, and no heat will be generated as a result.

It may also be possible that the heater control valve or the switch itself have malfunctioned. The heater control valve is the component that physically allows coolant to flow from the engine to the heater core, and the switch, the physical set of knobs that controls the system.

If either of these get stuck, leak, or otherwise malfunction, they can cause the system to not produce heat. Also be aware that issues with the heater are issues with the cooling system, and as such can sometimes cause overheating. I would start with checking the coolant level, when the engine is cool, and proceed from there. If you would like to have this checked, a certified technician from YourMechanic can come to your car’s location to diagnose the heating problem so that this can be addressed.