Stop= cold.... go= hot
1 Answer
That can be due to something as simple as being low on coolant. You get heat from the heater core when car is moving because you are revving the engine higher, so the coolant is being forced to circulate faster. Then when you stop and engine drops back to idle the coolant flow slows or stops. So check your coolant level! If you find the coolant level is good, then the problem may be with the water pump, restricted radiator, or restricted heater core (you'll have to run tests to determine what is wrong).