How To Replace A Fan Motor In A Central Air Conditioner's Condensing Unit

Does your central air conditioner cycle on and off before reaching the desired temperature? When you stand next to the condensing unit outside your home, does the unit sound eerily quiet when it's supposed to be running? The likely cause of your problems is a failing or failed fan motor.

The condensing unit needs a fan because the refrigerant phase change that happens inside the coils needs cooler air to both facilitate the change and keep the unit from overheating and shutting down. The easiest way to fix a broken fan motor is to call in an HVAC technician. But if you have some do-it-yourself experience and know where to order the new part for your unit, you could easily have the change done in one afternoon.

The following instructions are a general guide on replacing a fan motor in the condensing unit. Consult your owner's manual for specific directions as the details, such as the location of certain parts, can be different depending on the unit. You also need to completely turn off the power to your unit before working. Cut the power by either removing the fuses on the box near the unit or by flipping off its circuit breaker.

What You Need:

  • Screwdriver
  • Razor Knife
  • Wrench
  • Socket wrench
  • New motor
  • Zip tie

Step 1: Unhook the Wires 

Start by unhooking the bottommost part of the motor, which are the wire bundles that can be reached through a side access panel on the exterior of the condensing unit. Use a screwdriver to remove the fasteners for the panel and then remove the panel door and set it aside.

You should now see two bundles of wire that come together at a middle segment that looks a bit like a plug. The bundles are likely held together with a zip tie. Using extreme caution, cut off the zip tie using a razor knife. Unhook the two segments of wire from each other and let them both dangle for now. You don't need to keep track of individual wires to know which bundle is actually attached to the motor since the appropriate wires will simply lift away with the motor when the time comes.

Step 2: Remove the Motor Assembly

Leave the side panel open and move your attention to the top of the condensing unit, where you should see a grated fan guard that has a bit of a bubbled shape. Remove the screws holding the fan guard to the top of the condensing unit.

The fan guard is the uppermost part of the motor assembly followed by the motor and then the fan blades. Lift the fan guard up and flip the assembly over and the fan blades should now be on the top. There might be a safety wire attached to the guard to keep everything in place. Simply pull off the wire and leave it dangling for now.

You can now reach down into the unit to find the end of the wire bundle and pull it free of the hole that passes out into the access panel. The wire bundle will also need to pass through a hole near the top of the condensing unit that is simply there to help hold the wires into place. Pull the wires completely free and you can then pull the entire assembly free from the condensing unit.

Step 3: Remove and Replace the Fan Motor

Use a wrench to loosen the screw holding the fan onto the motor. Remove the fan blades from the spindle on the motor. If the fan itself isn't damaged, you can reuse the fan on the new motor. If the fan is damaged, you will want to use a new one on the new motor.

Remove the wire guide over the wires attached to the motor. The guide looks like a rubberized casing and it unsnaps fairly easily for removal.

Use a socket wrench to remove the fasteners connecting the motor to the fan guard. Now you can position the new motor exactly where the old motor was just removed. Use the same fasteners to fasten the new motor into place on the guard.

Step 4: Hook Things Back Up

Place the wire guide over the new bundle of motor wires and snap it shut. Reattach the fan blades onto the motor's spindle using the original set screw. Make sure the screw is tight so that the fan doesn't fly off when the unit is turned back on. 

Now you're ready to put the motor back into the unit. First, feed the wires through the hole near the top of the unit and then through the side hole where the access panel was located.

Flip the guard back over and place it on the condensing unit so that the fan is on the bottom and the guard is on top. Reattach the fasteners for the guard.

Head back to the access panel and plug in the two sections of wire. Place a new zip tie over the wires to bundle them together for neatness and ease of access in the future. Replace the access panel and its screws.

Turn power back onto your unit and test to see if the fan works. If it doesn't, call in an air conditioning units repair service.