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Central Air Unit Problems

What is a central air unit?

A central air unit is one that circulates cool or warm air through a room or rooms of a house. They are of 2 types – split system or packaged units. In the split system the outdoor unit contains the compressor and condenser and the indoor unit the evaporator and heat pump, if one is fitted. In the packaged unit the complete system is place outdoors and the air is circulated indoors through ducts. More information on central air units may be had at the Department of Energy website.

My Carrier model 24ABR336A0031010 central air unit is not working. It seems the outside fan is the problem. It spins freely when I move it by hand, but the motor is hot to touch and does not move with the power on. Can you tell me what to do?

From the symptoms, it appears likely that the fan motor bearing is bad. When the bearing is worn it gets egg shaped. It will turn by hand but when the power is on, the misshapen bearings allow the rotor to pull against the windings, causing it to lock up. If you are comfortable with working on electric motors you can try to replace the bearings yourself. Otherwise, it is advisable to get a technician to do the job.

My central air unit with a heat pump keeps blowing the fuse on the indoor disconnect box when I try to start it. What is the problem and can I fix it myself?

From the description of the problem it appears that the problem is either with the motor, compressor or relay. These are not central air unit problems that a layman should tackle. I suggest you call a technician to check the unit and to the repairs.

My central air unit does not shut off and the house keeps getting colder and colder. The thermostat on the wall is tilted. Could that have anything to do with it?

It looks like you may have spotted the problem. If it is a mercury bulb thermostat it must be perfectly level to function properly. Any tilt will affect its accuracy and ability to control temperature. This is an easy repair. Turn off the power and remove the unit from the wall and check to see if the screw is stripped. If so it cannot hold the thermostat in place and needs to be replaced. While the unit is off the wall, check if there is a gap in the hole in the wall where the wires emerge. If there is, sealing it up will improve the accuracy of the thermostat. If you need to disconnect the wires, put a piece of masking tape around each one and write the terminal marking - R, C, Y, G etc. on each wire so you know where to reconnect it. Once the reconnection is done use a small level to ensure that it refitting is done so that the unit is perfectly level. This should solve your problem.

I recently replaced the furnace on my Carrier central air unit. The new furnace is not working. When I checked I found 2 wires to the outside unit not connected. I can’t get hold of the installation guy. Please help.

This is an easily resolved problem. Connect the Y (yellow) wire to the thermostat and the other one to the C connection on the control board. Make sure the furnace door is closed. There is a door switch the will prevent it from operating of the door is open. The furnace should now work.

My Central air unit has stopped cooling and is now blowing out warm air. I replaced the thermostat but it made no difference. Are there things I can check myself before calling technician?

There are a few things you can do. First set the thermostat to a temperature that will cause the cooling to start. Then go to the outside unit and see if the compressor is running. You should be able to hear it. Also look inside the unit to see if the compressor has iced up. This can happen in very humid conditions. If the compressor is running and not iced over, turn off the power and check the fuses in the fuse box located near the condenser on the outside unit. Replace any blown fuses with ones of the same rating. If the problem persists, it is likely that the system is low on coolant. This is something that can be checked only by a technician using special equipment. Please call in a technician to check the unit.

Because it is a complex piece of machinery, there are many potential causes for central air unit problems. If the troubleshooting guide in your owner’s manual does not resolve your problem, it is advisable to get expert help rather than risk making the situation worse.
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