Electric Motor Troubleshooting

• Disconnect power to the motor before performing service or maintenance.
• Discharge all capacitors before servicing motor.
• Always keep hands and clothing away from moving parts.
• Be sure required safety guards are in place before starting equipment.

Motor fails to start upon initial installation.

• Motor is mis-wired. Verify motor is wired correctly.
• Motor damaged and rotor is striking stator. May be able to reassemble; otherwise, motor should be replaced.
• Fan guard bent and contacting fan. Replace fan guard.

Motor has been running, then fails to start.

• Fuse or circuit breaker tripped. Replace fuse or reset the breaker.
• Stator is shorted or went to ground. Motor will make a humming noise and the circuit breaker or fuse will trip. Disassemble motor and inspect windings and internal connections. A blown stator will show a burn mark. Motor must be replaced or the stator rewound.
• Motor overloaded or load jammed. Inspect to see that the load is free. Verify amp draw of motor versus nameplate rating
• Capacitor (on single phase motor) may have failed. First discharge capacitor. To check capacitor, set volt-ohm meter to RX100 scale and touch its probes to capacitor terminals. If capacitor is OK, needle will jump to zero ohms, and drift back to high. Steady zero ohms indicates a short circuit; steady high ohms indicates an open circuit.
• Starting switch has failed. Disassemble motor and inspect both the centrifugal and stationary switches. The weights of the centrifugal switch should move in and out freely. Make sure that the switch is not loose on the shaft. Inspect contacts and connections on the stationary switch. Replace switch if the contacts are burned or pitted.

Motor runs but dies down.

• Voltage drop. If voltage is less than 10% of the motor’s rating contact power company or check if some other equipment is taking power away from the motor.
• Load increased. Verify the load has not changed. Verify equipment hasn’t got tighter. If fan application verify the air flow hasn’t changed.

Motor takes too long to accelerate.

• Defective capacitor. Test capacitor per previous instructions.
• Faulty stationary switch. Inspect switch contacts and connections. Verify that switch reeds have some spring in them.
• Bad bearings. Noisy or rough feeling bearings should be replaced.
• Voltage too low. Make sure that the voltage is within 10% of the motor’s nameplate rating. If not, contact power company or check if some other equipment is taking power away from the motor.

Motor runs in the wrong direction.

• Incorrect wiring. Rewire motor according to wiring schematic provided.

Motor overload protector continually trips.

• Load too high. Verify that the load is not jammed. If motor is a replacement, verify that the rating is the same as the old motor. If previous motor was a special design, a stock motor may not be able to duplicate the performance. Remove the load from the motor and inspect the amp draw of the motor unloaded. It should be less than the full load rating stamped on the nameplate.
• Ambient temperature too high. Verify that the motor is getting enough air for proper cooling. Most motors are designed to run in an ambient temperature of less than 40°C. (Note: A properly operating motor may be hot to the touch.)
• Protector may be defective. Replace the motor’s protector with a new one of the same rating.
• Winding shorted or grounded. Inspect stator for defects, or loose or cut wires that may cause it

Motor vibrates.