Thread: Cold air from heater

My friend's heater blew cold air. He already put a heater core in it. Could it be that the heater core was clogged up or something else must have gone wrong?

Is this a heat pump system? With a heat pump, the outside compressor runs for heating as well as cooling, and you do not use gas or oil. It sounds to me like it is a heat pump getting its signals crossed and setting the control valves to cooling when it should be heating. When it fails to heat the house, then the resistance elements, ''em heat'', kicks on. There could be several things causing the problem. If you are lucky, it could be bad connections between the thermostat and system. Check them paying particular attention to orange, black, and brown wires and anything connected to a O or O/B terminal.

The control valves could also be bad or the control board for the system. The control board isn't too bad to change, but it could be an expensive gamble if you aren't sure it is the problem.

I am afraid if you don't find a loose wire or something, you may have to call back the repair man. You could post back here with any more info you have, but I am not sure anybody here will be able to help.

Was the whole system full of junk? If so, it could be that it didn't flush out well, as a result it clogged. Try to check if the hoses feel too warm to hold or if this has a heater control valve. Have you replaced anything?

There must have been something wrong with its control valves when your friends installed it. Why not check that out and let us know.