This write up is about how to test your relays. A relay is a switch used to turn things on and off. If you suspect a relay of being bad, testing it is a easy straight forward process. You will need a multimeter.

Remove the relay from the car and place on your work bench.

Switch your multimeter to the lowest Ohm setting.

Look on the sides of the relay. There should be a picture showing the type of relay you have. This image shows a normally open relay.

Others can be normally closed.

This image shows a switched relay where pin 4 is normally closed, and pin 5 is normally open. This is the relay we will be using in this lesson.


Now look at your pins. There will be numbers showing each pins number. The location of the pins will not always match the image on the side, so only note the numbers.


Now first test the control circuit, this is pins 1 and 2. Connect your tester to these to pins. You want a reading between 50 and 120 Ohms. Less then 50 and the relay is suspect.


Now we will test between pins 3 and 4, this is the normally closed circuit. You should have a <1 ohm reading.


Now test between pins 3 and 5, this is the normally open circuit. You should have infinity. This indicates the relay is open.


This covers the basics of a relay test. To finish testing the relay you will need to connect a DC power source to the control pins. Before doing this make note of the pins. Some relays have a diode and connecting the + and - backwards will damage the relay. Once you connect the power you will here a click. This will indicate the relay has moved. You will still need to test the Ohms across the pins. Check that a normally closed relay is not reading infinity, or a normally open relay is reading <1 Ohm.

Once completing these tests, you will know for sure if the relay is good, or bad.