Heater will not blow warm air when car is stopped or parked, but will when moving. on 2007 Chevrolet Uplander

when I am moving down the road the heater works fine at every setting, but blows cold air when stopped at a light or parked.

also rear air quit blowing all togeather. where is the rear air blower located on my uplander or is there another problem?

Asked by for the 2007 Chevrolet Uplander
Check your engine coolant level, it's probably low. Your heater core uses the heat off of your engine provided by your engine coolant.
1 more answer
Sounds like you are low on antifreeze. If the level is low, the car does blow cold when the car is idling. Most likely this is an inexpensive fix that should remedy your problem.