How to Diagnose a Failed Relay In Your Car, Truck or SUV

Learn how to diagnose a failed relay in this video! So, your horn won't honk, or your headlights won't light. You checked the fuses, and they look fine! What's going on? Time to check the relays! Watch this video to find out how a relay works, what can go wrong with one, and ways you can check yours to see if you need to replace it!

Check out our list of many other diagnostic videos!

How To Use a Multimeter:

⚠ DISCLAIMER:
While 1A Auto strives to make the information provided in this video as accurate as possible, it makes no claims, promises, or guarantees about the accuracy, completeness or applicability of the content. No information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. All do-it-yourself projects entail some risk. It is the sole responsibility of the viewer to assume this risk. 1A Auto is not responsible or liable for any loss damage (including, but not limited to, actual, consequential, or punitive), liability, claim, or any other injury or cause related to or resulting from any information posted in this video.

[AAuto]

√ *Watch the Video*
√ *Do it Yourself*
√ *Save Money*

[SChicken]

This is hands down one of the most informative channels for automotive!

[JCsaysSPAYNEUTERVOTEandMAKEART]

Best company ever. Sells the parts, shows you how! I've replace a ton of things on my car, including all window switches and all regulators. Thank you 1A!

[buddyholly]

Without this channel my truck would live at the auto mechanic shop. That’s not including the thousands I would spend. Absolutely love this channel

[SrnDpT-tixs]

LOVE the thorough explanation for how it works!!! Common sense explanations and down to earth testing for amateurs without expensive toys. LOVE LOVE LOVE IT

[janeene]

YouTube has saved me so much money on car repairs! 🙌🏾

[pyrokamileon]

thank you very much for making this video! I tried reading a write up explaining how relays work and I wasn't grasping everything very well. but now that I have seen this video it all makes a lot more sense to me, it may be just that it's one of those things that you have to see in motion to understand better.. thanks again! 😀

[WalkOverHotCoal]

Thank you for your video. That would have to be one of the best for a novice like myself. Now I can diagnose electrical faults with more confidence. Great job sir.

[TheMotorPsych]

Very well explained different methods of testing relays; really liked how you took the time to explain the workings too. Great for amateurs like me.Thanks!

[Mr.C.Cloud]

Best auto repair video ever. Stumbled upon this trying to figure out why my Ford Focus high beams aren’t working but I hear a click! ✔️✔️✔️✔️✔️✔️✔️✔️✔️✔️✔️✔️

[TENCUHTLI]

I really love the horn animation, that’s Disney level of creativity!

[lylachristopherson]

LOL. BEST DESCRIPTION, EVER!! Thank you. Also, I loved the "Honk Animation". I watched it five times. You made little animated sound waves, and the relay actuator closed! Brilliant!

[mymusic]

A relay is the first video I've seen to bring this tool up into the discussion! Also very good explanation of how a relay works. A helpful and informative video! 👍

[jeffreydaley]

Excellent video & detail. Like the fact you demoed other methods of testing. Thanks.

[CoolHandLuke]

I knew their had to be a way to test those. The Chevrolet dealership and stupid autozone said they can't test them! BS! Thank you! You saved me 50 bucks! My issue is my more expensive radiator but that 50 will go towards them. Thank you again.

[adamgerald]

Here's some advice for fixing this for free. Yeah they're cheap but you may get stranded and need to fix it.

I had a ranger that sometimes wouldn't start. Everyone kept telling me it was a bad fuel pump. It worked fine on a cold start, but if I turned it off after it warmed up, and tried to start it back, the fuel pump wouldnt come on. I managed to find out that when the engine bay warmed up, the relay wasn't engaging. I did this by swapping the relay with something else and trying it. I then, being completely broke, cut open the top of my relay and saw one of the contacts near the coil of copper wire (electro magnet) was bent slightly away from the coil. I pushed it back straight, and taped up the relay housing good to keep dirt out of it, and bam. worked like a charm for the entire rest of the time I owned that truck and it cost me nothing. and if I'd listen to everyone else I'd have wasted time and money on replacing the fuel pump. The reason I didn't think it was the pump is because it was intermittent and only when the car had warmed up, and it never acted up while driving, only if I shut it off then tried to start it again.

Long story but I'm telling it so people know a relay can be intermittent. If you're not sure what to do, mark it with a sharpie (so you know which one is the original) and swap it with another relay and see if the problem follows or not.

[alewis]

Thanks for explaining, showing, and testing the relay.

[annam]

The diagram made easy to understand how a relay works. Thank you!

[SCESW]

Thank You so much for this video.
It helped me sort out something that had been driving me crazy.
Did not realize that inserting it backwards will 'randomly' break stuff.

[jembo]

That has to be the best and so well explained video on how a relay can be either bad or good. Thanks so much for your great explanation. Top class.