Heater blows cold air while idling but hot air when driving. Why?
My 2004 Nissan Titan heater blows cold air while idling but hot air when driving. At first it
would only blow cold air but I found that the coolant level was low - I believe I have a slow
leak in the upper part of the radiator. After filling the radiator, I could get hot air but only
with the engine revving or while driving. Any ideas?