How to Repair a Burnt AC Motor

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If your AC goes out in the summer, expect to be sweating. In the middle of summer, there are few bigger calamities than having your air conditioner (AC) malfunction, particularly in the middle of a heat wave. If the motor burns out, you may need a professional to replace it. If you catch the problem in time, however, you may be able to repair it yourself if you have experience disassembling and fixing electrical motors.

Difficulty:Moderately ChallengingWrench setsMultimeterScrewdrivers1

Observe your AC motor. If you smell heated metal or oil, a lack of lubrication may be causing the problem. If the odor is more sour, the belts may be faulty. Bearings may be the culprit if your engine is grinding, and something may be blocking the ventilator if you can't even touch the AC motor because it's so hot.

2

Open up the AC unit and find the motor. The specific location varies by manufacturer, so consult the instructions that accompanied your system. Go to your main circuit board and turn off power leading to the HVAC system. If it is not labeled, you may need to turn the entire board off, shutting off all power to the house. If your motor isn't working, you may not be able to isolate the proper circuit by trial and error. If the motor turns back on while you're working on it, the risk of electrocution is extremely high.

3

Look for any ports marked "oil" on your AC motor's exterior. If you smell hot plastic, metal or oil, your motor may not have enough lubrication to operate correctly. Add lightweight straight oil to these ports. Check your instructions that came with your AC unit to determine the specific amount of oil to add.

4

Open the motor following the instructions published by your AC motor's manufacturer. Set your multimeter to RX1, and hook one probe to the white lead. Connect the other probe to the other wires coming from the motor. If you get a reading of zero resistance, or infinity, the system has a short somewhere. A low reading indicates that the operation is within tolerances. If the motor has a short, you will spend a lot less time and money replacing the motor than repairing it, so look in the instructions to find which type of motor you should buy. If the reading is within acceptable tolerances, move to Step 5.

5

Examine the belts inside your AC motor. If they have significant cracking or discoloration, they must be replaced. Use the setscrew to loosen the belt enough to remove it, and then to tighten the new belt into place. If the motor has been hot to the touch, move to Step 6.

6

Look at the blades on the fan that cools your motor. If any of them are damaged, replace them. A broken blade can cause your motor to spin out of balance, causing further damage inside the motor.

7

Put the motor back together and turn the electrical power back on. If these steps do not work, call a licensed HVAC technician to solve the problem.

Check your homeowner's insurance policy and your home warranty policy to ensure that you will not be invalidating coverage by attempting repairs without a license.

If you are electrocuted while working on your AC motor, the consequences could be deadly. If you have uncertainty about whether current is running into your HVAC system when you are ready to work on it, it's better to turn off power to the whole house.

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