Electrical Systems

Step 1 — Safety

• Turn power OFF at isolator or breaker

• Confirm the motor is not live

Step 2 — Identify the motor wires

• Find the 3 motor terminals or wires:

  • C = Common

  • R = Run winding

  • S = Start winding

Step 3 — Disconnect the capacitor

• Remove 1 capacitor wire from either side

• This stops the capacitor from affecting your readings

Step 4 — Set your multimeter

• Set to Ohms (Ω) mode

Step 5 — Test all 3 winding paths

• C ↔ R → checks the run winding

• C ↔ S → checks the start winding

• R ↔ S → checks both windings in series

Healthy motor windings will show

• A resistance number on all 3 tests

• C↔R = lowest Ω → normal

• C↔S = higher than run Ω → normal

• R↔S = highest Ω → also normal when the capacitor is disconnected, because this is both windings in a loop

Important note

• R ↔ S will always show the highest resistance when the capacitor is removed

• This is correct and does not mean the windings are faulty

Check for shorts to ground

• Test each wire (C, R, S) to the motor’s metal body

• No reading / no beep = PASS

• Beep or a number = FAIL (short to motor body)

Fault signs

• OL (no reading) on C↔R or C↔S → broken winding → FAIL

• 0Ω or near 0Ω → shorted winding → FAIL

• OL on R↔S only → capacitor circuit open (windings can still be OK)

Final result

• If windings show resistance and nothing connects to the motor body → windings are healthy

• If any winding test fails → motor needs repair or replacement