Troubleshooting Magnetic Contactor Problems

Two magnetic contactors on a white background.
  • 2 hours
  • Intermediate
  • 20
What You'll Need
Non-conductive cleaning solution
clean wiping cloth

Electricity travels in circuits, and in the heart of those circuits are magnetic contactors designed to keep everything running smoothly. But the system can jam from time to time. Although you should never try fixing problems that have something to do with electricity if you do not have the proper training and skills, troubleshooting a faulty contactor isn’t impossible. If you aren’t comfortable working with these components, hire a professional who can fix it for you.

Open Circuits

The very first thing that you should check is if the contactor coil can still move the contact assembly. If the answer is no, you may have an open circuit keeping the power from reaching and activating the coil. To be really certain, check the voltage at the coil terminals while it should be turned on. If the voltage is present, turn off the power by unplugging from the wall outlet or by shutting the circuit breaker down. Remove the wire from one of the coil's terminal, and setting your multimeter in a low ohm range, check across both terminals and if you read very high resistance or up to "∞", the coil is open and needs replacement.

Holding Does Not Close

If the problem isn’t because of an open circuit and the mechanism can be heard "clicking" ON, check the holding contact for continuity, since it is through this contact that the coil will remain activated. If the sealing circuit does not close, the cause could be from damaged or burnt contacts or any loose wiring connections in the contactor auxiliary contacts. Normally, the contactor holding should close when there is power.

Physical Barriers

If the reason why the sealing circuit does not close is because of any physical barrier that isn’t a safety feature such as dirt or dust, then simply remove it. You want to make sure that you unplug it or turn off the breaker to keep safe. You may want to keep your circuits secure from the elements to prevent anything else from getting caught in the sealing circuit.

Voltage Variations

Now check the magnetic coil’s voltage. If it fluctuates from time to time, the branch circuit may be experiencing voltage variations.

Dirty Assembly

A sticky magnetic assembly can actually cause technical problems. If this is the case, correct the problem with a non-conducting cleaner.

Intermittent Operations

Overload relays are actually vulnerable to intermittent operations. This problem occurs when the overload relays do not stay closed. Overload relays are often vulnerable to getting tripped. One possible scenario could be that excessive heat generated by a motor has caused the overload relay to trip, thus cutting off the power to the relay.

Another angle could be that the heat has prompted your motors to work a lot faster. Your overload relay will be able to notice this change and trip itself in an effort to protect the entire system from being further damaged especially the motor. In this case, you need to set up a system where the motor receives appropriate ventilation.