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How to Fix a Noisy Blower Fan in a Condensing Unit

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The outdoor condensing unit half of your central air conditioner contains a motorized fan that circulates air to prevent overheating. If the fan stopped working, you would know because the unit would overheat and trigger a self-protection shutdown mode. But sometimes a fan simply becomes noisy while otherwise working normally.

What causes the fan to become noisy? The fan blades could have become bent or broken, but the more common cause is simply that the blades became loose on the motor assembly. If you are sure the fan doesn't have any structural problems, you can fix the noise yourself, but you should leave more advanced repairs to an appliance repair or air conditioning services company.

What You Need:

  • Socket
  • Screwdriver
  • Adjustable Wrench

Step 1: Prep the Unit & Access the Fan

Turn off power to the condensing unit by pulling out the fuse in the fuse box on the wall near the unit. Locate the grated, domed fan guard on the top of the condensing unit. Use a screwdriver to remove the fasteners surrounding the guard then place the fasteners in your pocket for safekeeping and easy access.

Lift straight up on the fan guard to pull the fan assembly clear of the top of the condensing unit. Turn the entire fan assembly over so that the guard can rest on the top of the unit while the fan blades point straight up.

Step 2: Inspect & Tighten the Fan

Examine the blades for signs of breaks or bends. If you spot damage, call in your HVAC tech for repairs and don't run the unit until after replacing the blades. If the blades look healthy, you can continue with your repairs.

Use your hand to gently turn the fan blades around in a circle and check to see if the blades move smoothly around the motor drive shaft. If you experience an unexpected resistance, the motor might have a problem that could contribute to the noise. Call an HVAC tech to examine and replace the motor, if necessary.

Do the blades turn around without resistance but wobble as you spin? The fan blades simply need to be tightened. Locate the set screw on the side of the fan blades and tighten that screw with your adjustable wrench. Test the spin ability again to make sure the wobble went away.

Step 3: Put the Unit Back Together

Flip the fan guard back over so that the fan assembly goes down into the condensing unit. Position the guard in place using the mounting screw holes on both the guard and the unit as a guide. Reattach the fasteners to secure the guard into place.

Restore the power to your unit. Turn on your thermostat to trigger a cooling cycle and listen to the fan. If the problem was solved, you have finished and can celebrate. If you still hear the noise, you need to call a HVAC sales company like Triad Heating & Cooling Inc.