Cleaning and Maintaining the Magnetic Contactor

Cleaning and maintaining magnetic contactors (MC) are fairly easy and fast. Tools needed are usually screwdrivers, brush, rubber eraser (use the plastic rubber type, not the powdery rubber one). You can also spread a light colored material usually bond paper to contrast small items that comes from the magnetic contactor itself and small tools.




Start off by cleaning the outside of the MC with a brush. You can also use a high percentage ethanol solution to clear out contacts. (Ethanol is highly volatile and flammable so keep it away from flames and sparks!)




Unscrew the screw that holds the upper and lower parts together of the MC. Sometimes a locking notch at the opposite side from which the screw was found helps keep the upper and lower parts be together. This can be easily be disengaged using a flat screw driver.




Once the upper and lower parts are separated, the coil can be removed, the spring and the upper and lower cores. Check for corrosion and rust. You can use a rubber eraser to clean out minor surface problems on the cores or use an abrasive if rust has already settled. Check the resistance of the coil. It must be from a few tens of an ohms to more or less a hundred but should never be below or beyond by means of another hundred or more. Ohmic values of the core varies with the corresponding operating voltage of the coil.

Also check the resistance between the line side and load side of the terminal contacts of the MC. L1 and T1, L2 and T2, L3 and T3 should each have a resistance of less than an ohm, otherwise clean with a contact cleaner available in most of the industrial and electrical supply in your neighborhood.


After cleaning and making the necessary checks, put back the magnetic contactor ensuring that screws and locking notches are securely in place. Power up the said contactor with the correct operating voltage and check again the resistance. When power upped, always be careful of live voltages and ensure your safety first.