I have a problem where my civic (96 ex) cools off in the winter (minnesota) if it doesn't get completely warm. When i drive to class, my car will warm up fine if i keep the heat off, but if i pull up to a light and the car JUST hit normal temp and i turn the heat on, it starts cooling off. The heat coming out of the vents is warm but not hot. Same thing happens when i'm coming down from a mountain pass or long downhill. When i do drive for an hour or so, it takes about 5 minutes after my car is at normal temp for the heat to get really warm. This happens when outside temp is in the teens. It hasn't gotten really cold here yet though...so i'm afraid of what will happen then. The car never gets any hotter than it should though. Can a thermostat open at the right temp and close at the wrong temp? It seems like the thermostat won't shut when the car starts cooling off. If it's a really long light, the car can almost completely cool off with the heat going. Does this happen to anyone else? I hate that my roommates crappy taurus heats up in 3 blocks, but i have to drive across town before my car is comfortable.

 

Yeah, it definitely looks like thermostat not completely closing problem. Just replace the damn thing, this should help.