Checking the health of the relay

The principle of operation of the relay is based on the closure of contacts under the action of an electromagnetic force that occurs in the coil when an electric current passes through it. Therefore, to test the relay, it is necessary to apply voltage to the terminals of the relay coil winding and measure the resistance between the terminals of the contacts (see photo).



If the relay is OK, there will be a click and the resistance will be close to zero (infinitesimal). Otherwise, the relay is defective and must be replaced.