How to test a relay

This article shows you how to test a relay. A relay will usually have a coil, pole terminal and a set of contacts. The set of contacts that are open when the relay is not energized are called normally open (N/O) contacts and the set of contacts that are closed when the relay is not energized are called normally closed (N/C) contacts. The following steps can be used to perform the testing of the relay using a multimeter.

• Keep the multimeter in the continuity check mode.
• Check for continuity between the N/C contacts and pole.
• Check for discontinuity between N/O contacts and the pole.
• Now energise the relay using the rated voltage. For example use a 9V battery for energising a 9V relay. The relay will engage with clicking sound.
• Now check for continuity between N/O contacts and pole.
• Also check for discontinuity between N/C contacts and pole.
• As a final test, measure the resistance of the relay coil using a multimeter and check whether it is matching to the value stated by the manufacturer.

If all the above tests are positive we can conclude that the relay is healthy.