Inside your outdoor AC unit, there is a motor that drives a fan, which in turn creates airflow for the system to function properly. Inside the assembly are start capacitors, to provide the energy needed to start the fan, and run capacitors that keep it running. There are a few signs of an outdoor AC fan motor problem. Here, we’ll cover these and how to check and test the motor to determine if repairs are needed.

Common AC Fan Motor Issues


  • The Fan Won’t Spin: If the unit isn’t humming, this means the blades aren’t spinning (but if you do hear a hum, there’s a capacitor issue). Check whether the compressor is working. If so and the fan won’t work, the motor and/or capacitor need to be serviced. However, if the compressor isn’t making any sounds, there could be a faulty contactor. Also, check whether the unit is powered.
  • The Fan Is Slow: Check for a loose fan blade or a burnt-out heat pump compressor pump. A circuit on the control board may have failed. This often includes low-voltage components. You’ll need an HVAC technician to perform repairs regardless of what’s causing the fan to run slower.
  • The Fan Is Noisy: If you hear humming, buzzing, or ticking, check whether the fan blade is obstructed. An imbalanced or damaged condenser fan can cause a humming sound. If it’s balanced and in good condition, a bearing or capacitor may be malfunctioning.
  • The Fan Blades Are Loose: If the fan isn’t working right and the blades seem loose, turn off the system and check if the blades are bent, cut, or loosely connected to the motor shaft. You can usually push a small bend back into place or tighten loose screws, but other issues must be addressed by a professional.
  • The Fan Short Cycles: If the fan keeps tripping the thermal overload switch, it will turn off. This can mean there’s a short in the motor windings. If so, the motor will run after you disconnect the capacitor.

Steps to Checking the Outdoor AC Fan Motor


When the fan motor doesn’t seem to be running, follow these steps to troubleshoot the problem:

  • Check the thermostat to see if it is turned on.
  • Look for a tripped breaker at the main service panel.
  • Replace the air filter; dirt and debris can block airflow and affect the motor.
  • Examine the fan to see if the blades are turning or not.
  • If they’re obstructed, unblock the fan blades using a screwdriver or similar tool.
  • Give the blades a push; a kickstart can get the motor working once you turn the AC back on.
  • Inspect the capacitor visually and with a capacitor tester. If you’re not experienced or comfortable with this, call a professional for help and to avoid a shock.

You can also troubleshoot a fan motor by testing the windings with an ohm meter. A 120V fan motor has black, blue, red, and yellow wires, plus a white wire, black wire, and two brown wires. Check the resistance between the white wire and each colored wire. If it reads zero, the motor winding may have a short. An infinite reading can mean the motor winding is open.

Call an HVAC Technician to Service Your Outdoor AC Fan Motor


Customers trust Tri County Air for high-quality HVAC repair. Our trained technicians are professional, courteous, and able to quickly diagnose and repair any AC component. Whether there’s an electrical, mechanical, or other issue, we can get your outdoor AC fan motor working again. To schedule residential HVAC services in Sarasota, Manatee, and Charlotte Counties, request your appointment online or call (941) 485-2222.