Wireman · Condenser fan won’t spin: troubleshooting for electricians · 2023 NEC ·

Condenser fan won’t spin

Bearings, the FAN side of the capacitor, voltage at the motor, then the windings.

Before you start

How much electrical experience do you have?

This sets how much detail each step shows. You can change it any time.

How it works

Most condenser fans are PSC motors: a run winding, a start winding and a run capacitor that stays in the circuit. The capacitor is usually the FAN section of a dual capacitor shared with the compressor. The motor gets 240 V from the contactor load side and has an internal thermal overload that opens when it gets too hot. Some newer units use ECM fan motors, which have their own electronics and no capacitor.

Step by stepFull flowchart

Every question and answer in this guide. Tap “Step by step” to walk through it.

What does the fan do while the compressor is running?
- Hums, blade doesn’t turnWith power locked out, spin the blade by hand. How does it turn?
  - Stiff, gritty or stops right awayWorn fan motor bearings
  - Spins freely and coastsTest: Test the FAN side of the capacitorExpect: Within the tolerance printed on the label, often ±5% or ±6%. A 5 µF section at ±6% should read about 4.7 to 5.3 µF.
    - Low, open or bulgedWeak or failed run capacitor
    - Within the ratingTest: Check voltage to the fan motorExpect: About 240 V (or 208 V).
      - No voltage at the fan leadsBroken or burned fan wiring
      - Full voltage, motor does nothingTest: Test the fan motor windingsExpect: Steady readings on every pair, with the highest equal to the other two added together. OL to the frame.
        OL on one or more pairsOpen winding or open internal overload
        Reads to the frameFan motor winding shorted to the frame
        All readings normalMotor fails under load
- Turns slowlyTest: Test the FAN side of the capacitorExpect: Within the tolerance printed on the label, often ±5% or ±6%. A 5 µF section at ±6% should read about 4.7 to 5.3 µF.
  - Low, open or bulgedWeak or failed run capacitor
  - Within the ratingTest: Check voltage to the fan motorExpect: About 240 V (or 208 V).
    - No voltage at the fan leadsBroken or burned fan wiring
    - Full voltage, motor does nothingTest: Test the fan motor windingsExpect: Steady readings on every pair, with the highest equal to the other two added together. OL to the frame.
      - OL on one or more pairsOpen winding or open internal overload
      - Reads to the frameFan motor winding shorted to the frame
      - All readings normalMotor fails under load
- Completely silentWhat kind of fan motor is it?
  - PSC (uses the capacitor)Test: Check voltage to the fan motorExpect: About 240 V (or 208 V).
    - No voltage at the fan leadsBroken or burned fan wiring
    - Full voltage, motor does nothingTest: Test the fan motor windingsExpect: Steady readings on every pair, with the highest equal to the other two added together. OL to the frame.
      - OL on one or more pairsOpen winding or open internal overload
      - Reads to the frameFan motor winding shorted to the frame
      - All readings normalMotor fails under load
  - ECM (no capacitor)ECM fan motor: check power, signal, then the motor
- Runs a while, then stopsThe motor is tripping its internal overload