How to Test a 3, 4 or 5 Pin Relay - With or Without a Diagram

Here is a video on how you can test a Relay with or without a diagram. I cover 3.4 and 5 pin relays and all you need is a 12v source, a multimeter and a test light.

You may also find these other videos helpful:

[bradical]

9 years later and this is still the best explanation on youtube

[anthonylavallee]

Beats all the other confusing videos and written explanations. A big thank you is in order!!

[TheMessiah]

2024 the best and complete video on testing relays. Thanks man!

[DavidLorellHoskins]

This was an incredibly helpful video. Your diagrams, explanations, and the stability/positioning of the camera all made this so simple to understand. Thank you

[speway]

Incredibly detailed tutorial. Absolute love it! The only thing I would add is a brief description on what constitutes a ground. Thanks for your positive contribution to the Youtube community.

[TurboJohn]

I went to tech school for everything a/c, d/c and digital... but fifteen years later not using that knowledge had me lost helping my father with his truck. Your video was very easy to follow, and lit up the ol'
 brain again. Thank you so much!

[sammacnab]

I really like this guy ! I was having problems with my ac compressor. I followed his instructions and found the AC clutch relay was bad. Thanks so much for posting this ! You're a great teacher !

[Hoboappalachia]

This is the best video on relays and testing I have found on YouTube so far. Thank you! Keep it up.

[joecain]

Hands down best explanation I've seen anywhere

[ericb]

What a great teaching video. Thanks for putting in the time on making this for us to learn.

[JDnBeastlet]

Thank you for this easy to follow instructional video. I used it to test a relay - something I have never done before - and I found it failed the 4th step (the grounded test light did not come on when the relay was energized and powered).

Great job!

[willb]

Thank you! Out of the many videos on testing relays, yours is the only one I could find for those of us who have a relay that has no diagram or numbers at all. Much appreciated.

[Angeldenis]

I was just watching to learn about relays. I don't need to check any right now, but now I wanna kust go grab a relay from my car and practice. :) . Nice Video.

[KevinIndreland]

You're a genius....your videos are always a big help and you spell everything out for us. Thanks a million!

[actualsurfer]

We are not yet completely sure...there is one more test, With the 85/86 energized and 87 confirmed "hot", you now need to put that test light back on 87a to see if it is also "hot".

Because of your tutorial, thank you, I was able to diagnose my relay as bad.
In my case BOTH the 87 and 87a are hot with the relay engaged. Causing all kinds of problems for my motorcycle.

I tested it as Good but always traced the problem back to the relay. Did some more playing around with it and discovered my issue.

Thank you very much for taking the time to make this video.

[kellypeterson]

Fixed my mercedes using this video. Had 74 ohms on 85 and 86. Relays opened and closed just fine. When 85 and 86 were powered and circuit closed, 30 and 87 had erratic ohms from .05 to 34.00. Tested 5 relays and that was the only relay with that problem. Replaced and now cooling fan comes on. Great video.

[lukemartin]

This is the best video I've found on relay explanation. Thanks for posting.

[rentownnz]

Thanks man.... been a long time since I diagnosed auto electrics a bit rusty. told me exactly what my brain had forgotten in 2 mins flat! good stuff.... Fixed my wiring issue and all running again, but had to eliminate 4 relays to move forward! cheers again!

[hubertwilliams]

I just have to say this.. You are a huge inspiration .. You gave me so much confidence and knowledge.. My 2003 Expedition started with a check charging system late February since then .. I've install new alternator, alternator wiring harness, 2 idle pulleys, removed and cleaned tension pulley, checked all my fuses and relays installed new engine belt ..today I got my truck running again and the reason why it did not start was one of the cables going to the fuse box was disconneted

[Damienjking]

Another great video and an outstanding explanation. I would offer just one small word of constructive criticism for future consideration and I hope you receive this in the helpful way its intended. On the paper you layout the pin configuration and the wiring diagram which is very helpful to aid understanding. The one improvement I would recommend would be to make the wiring diagram match the actual pin layout. In other words, both the pin layout and the wiring diagram would have the pin numbers located in exactly the same place. This would make it easier for viewers with little electrical experience. I think this may be why a few people didn't follow what you were saying. Even with that small area for improvement, this is an excellent and thorough video. Thanks for your efforts.