Tracing a problem in a motor circuit can be a headache, unless you understand the basics for the motor starter. By following these tips, the headache can possibly be avoided.
Grab those safety glasses and place them where they belong, protecting your eyes. Disconnect all incoming power from the motor circuit. Check that the power is off by switching the volt-ohm meter to volts and placing the leads to the incoming power. The voltage should read 0.
Check all termination screws for tightness by taking the appropriate screwdriver and turning in a clockwise direction. Visually check all wires to confirm that none of them have a burnt or black discoloration on the insulation. If so, you will have to replace that section of wire or the entire wire to the motor.
Using your volt-ohm meter in the ohm position, check for continuity on the fuses that protect the motor starter circuit. There should be three main fuses if it's a three-phase starter combined with two or three control circuit fuses. If any of these, check for an open circuit, replace and double-check all wiring as describe in Step 2 above.
Observe the overload heaters that are positioned at the bottom of the motor starter. These can become weak or the mating surfaces corroded with normal operation. Remove each one individually and check the mating surface to the motor starter. If they are corroded, rip a small piece of emery cloth and use your slotted screwdriver to clean and polish the surface. The overload heater may be severely discolored a deep purple or blue. This can be a great indication of over heating. Clean the mating surface and replace all of the overload heaters.
Items you will need
- Safety glasses
- Volt-ohm meter
- Wire pliers
- Screwdrivers, Phillips and slotted
- Emery cloth
- Operation of a motor starter in a damp environment may cause excessive corrosion; an application of an anti-corrosion gel may be warranted after the repair.
- If the motor starter still is acting up, you may have to completely tear down the unit and replace the holding coil. Using your volt-ohm meter in the ohm position check the resistance of the coil. You should consult the manufacturer for the proper resistance reading of this coil, since certain voltage coils will have various resistance readings.