AC Heating Issue
 

I have a Honda Civic 2002. My car will not heat unless I am traveling over 45mph. I already had the thermostat replaced. I have no issues with the engine tempature. I am not over heating either. What could be causing this? I was just told by the dealership that it is a blown head gasket. I thought that would cause the car to overheat. What do you think is causing it. I think I just need a new heat pump. Are they tying to rip me off?

A bubble of air in the cooling system will cause this. (Eventually if the bubble is large enough the car will overheat, but the first symptom is the heater stops working at idle). Check that the radiator is staying completely full. Park on level ground, wait until the engine is cold, and remove the radiator cap. Do not just check in the white plastic tank. If not completely full, pour in pre-mixed coolant.

If the bubble keeps reoccuring, the cause is most likely the head gasket. Get the radiator completely full and start the engine (COLD) with the cap off. A bad gasket will usually make air or coolant bubble out of the radiator, more when you rev the engine.