Relays are crucial components in many electrical systems
but how can you be sure they're working correctly? Today, we'll walk through the process
of testing a relay to ensure it's functioning properly. A relay is an electrically operated switch
that uses an electromagnet to control the opening and closing of contacts
When no power is applied to the coil, there's a connection between pins 30 and 87A
but no connection between pins 30 and 87. When power is applied to the coil
this switches, connecting pins 30 and 87 while disconnecting pins 30 and 87A
Before we begin testing, it's important to disconnect all wiring from the relay
or remove it from its socket. You'll need a multimeter set to continuity
or resistance mode for these tests. Let's go through the steps to thoroughly test a relay
Step one is testing the coil. Set your multimeter to continuity or resistance mode
and test between terminals 85 and 86. If the meter shows continuity or resistance
the coil is likely good. If there's no continuity or resistance, the coil is faulty and the relay should be replaced
Step two involves testing the normally closed terminals. With your multimeter still set to continuity or resistance
test between terminals 30 and 87A. Continuity here indicates that the normally closed function
is working correctly. No continuity means this function is faulty and the relay needs replacement
For step three, we'll test the normally open terminals. Check for continuity between terminals 30 and 87
In this case, no continuity indicates that the normally open function is working as it should
If you measure continuity, this function is faulty and the relay should be replaced
If the relay has passed these initial tests, we move on to step four
testing the actual function of the relay when energized. Keep your multimeter on continuity or resistance mode
Connect one probe to terminal 30 and the other to terminal 87
Initially, you should read no continuity. Now connect terminal 85 to the negative terminal of a battery
and terminal 86 to the positive terminal. This energizes the coil and your meter should now show continuity
If it does, your relay is functioning correctly. If there's still no continuity
the relay is faulty and needs replacement. Understanding how to test a relay is essential
for maintaining and troubleshooting electrical systems. By following these steps, you can confidently determine
whether a relay is working properly or needs to be replaced, ensuring the reliability of your electrical circuits