[mark_h]

One of my Carrier air handlers outside is making a noise I don't remember hearing before. The heat inside the house seems to be working OK, and the fan in the air handler is turning silently like its supposed to. However, when the unit is running, probably every 3 or 4 minutes I hear a loud hum like an electric motor trying to come on and then it stops after just a few seconds. Then repeats again in 3 or 4 minutes. Im in NC and we had a snow storm last night which doesn't happen around here very often if anyone thinks that might have something to do with it. I can't see any ice built up or down inside the handler anywhere. I turned my downstairs unit off to make sure it wasn't helping to heat the upstairs and the unit making the noise seems to be heating on its own if that helps. Thanks for your help.

[KC13]

What you describe sounds like a compressor that unsuccessfully attempts to start, and is periodically cycling via the internal overload protector. If you have a heat pump system, the auxiliary heat is cycling to keep the room temperature close to the setpoint, but probably lagging by a couple of degrees. When the system "appears" to be running, does the larger refrigerant line feel warm? If not, the compressor is probably not running. Try this: Set the thermostat system selector to the emergency mode. Does the noise stop?

[mark_h]

It sounds like you're right. If I watch my thermostat, I notice the auxiliary heat cycles on occasionally. Also, the large line coming in doesn't feel warm at all. Should I shut it off until I can get someone to look at it or just let it run as it has been. Or do you have any other suggestions? Hit it with a hammer?

[KC13]

Set the thermostat system selector to the emergency mode. This will allow the system to heat as an ordinary electric furnace without risking further damage to your heat pump.