Q: The heater doesnt come on in my car sometimes.

Hello, The thermostat regulates the flow of the coolant in your car’s engine and controls when the coolant flows in and out of the motor from the radiator by opening and closing at specific temperatures. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. When the thermostat is stuck open it can cause the coolant to circulate constantly resulting in the motor never reaching the correct operating temperature. This will also impact the flow of coolant into the heater core which provides the warm air that is blown into the cab of your car. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.