How to Test a Turn Signal Relay
There are several ways to test a turn signal relay. Here are the three most common ways:
1) Replace the Relay
When looking at a turn signal relay, the first thing many vehicle owners notice is that it is one of many relays in this area that look exactly the same. Nine times out of ten, the relays not only look the same, they are the same in reality.
Double-check the part number and if they match, simply replace the relay. If the problem has “moved” to another area of the vehicle, the problem is in the turn signal relay. This is the easiest way to check for a bad turn signal relay and is almost foolproof.
2) 6 Volt Test
This is not a foolproof way to test a relay, but it will detect about 95% of problems. All you need to do is get a 6 volt battery and remove the relay from the vehicle. Connect the 6 volt battery to the two terminals and listen for a click.
If you hear the relay click, the relay is most likely good. However, if you do not hear the relay click, it is time to replace it. Note that this method is not completely foolproof, so if you have a multimeter, it is best to move on to the next test.
3) Check the Resistance
Look in any electrical troubleshooting textbook and you will find this method for testing relays. Just set up your multimeter to test resistance and connect it to the correct two terminals.
Look for a resistance between 50 and 120 ohms for the relay to function properly. If the relay reading is out of limits or has excessive resistance, it’s time for a new relay.
Also, note that if there is very little resistance, the relay may be stuck closed, which means you’ll need a new one as well.