no heat when car is not moving on 2002 Toyota Celica

My heater seems to work perfectly fine as long as the car is moving. If I stop at a light etc. for more than about 30 seconds cooler air starts to come out. Any ideas? Thanks!

Asked by for the 2002 Toyota Celica
Sound like you might have a partially plugged heater core. Try getting the cooling system flushed and see if that helps.
1 more answer , 1 more comment
check your radiator level, as stupid as it sounds my 01 celica didn't have heat for 2 years. I was thinking it was the heat flap or something because when I drove the heat would start working and when I stopped it would stop working. Yesterday the car overheated so I checked the antifreeze and added about half a gallon. The car stopped overheating and as a side result the heater started working normally again. I did head slap and went on with life. Most vehicles have the heater core low to the floor but in the celica it is actually higher than the motor which means if fluid is at all low it won't work as it turns out.
about a month ago I checked the antifreeze and it was pretty low, never overheated though. Filled it up and heat works perfectly again! I was happy it was such an easy fix!