How To Test Relays- EricTheCarGuy

How To Test Relays- EricTheCarGuy

How to test relays is a video about just what it says. Every once in a while you need to test a relay and when you do it's important to check it thoroughly, if not you may think it's good and it's not, just because it 'clicks' doesn't mean it's good because that's only part of the equation. Yes you can swap it out with a known good relay and that will save you time but if you don't have a known good then this test should do the trick for you. This video is also a good way to get to know what's inside a relay and how it works so if you're curious about that this would be a good video to watch.

If you want to see a video on basic electrical diagnosis click here.

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Due to factors beyond the control of EricTheCarGuy, it cannot guarantee against unauthorized modifications of this information, or improper use of this information.  EricTheCarGuy assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. EricTheCarGuy recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video.  Due to factors beyond the control of EricTheCarGuy, no information contained in this video shall create any express or implied warranty or guarantee of any particular result.  Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not EricTheCarGuy.

[SuperBIGGUY]

Im 21, I have 5 ASE's and work in a independent repair shop. I watch your videos in my free time trying to learn all i can. You really have helped me in the real world diagnosing problems and understanding systems. thanks for the videos you make!! it has made me a better technician! 

[SantanaLG]

EricTheCarGuy, I want to say thanks to this videos I was able to fix my car. My car was having a no spark because of bad ASD relay. Your process of testing relay is simple and effective. This video help me identify a bad relay that prevent my car from starting. Once again thanks:)

[coupes]

eric please do not ever retire .you make the best vids you explain everything in detail

[darrenfozziefoskett]

Thanx Eric TheCarGuy and Aaron Houk (couple comments below) Fixed the ole ladies car in less than 4 hours. That includes watching this and a few different vids, WALKING to the Hardware store, grabbing a Gerry can of fuel, changing the batteries in my flash light, a quick jaunt to the beer store, a conference with the neighbourhood guys (who saw a hood up and were drawn like flies to shit.... they didn't help, but drank my beer), and lastly actually doing the repairs. I'm a hero for less than an hour actual work. Keep up the great work.

[drakkarind]

Eric, thank you so much for a simple, yet comprehensive instruction on how to test one of these stupid things. I gotta say, your videos are some of the best. Unlike so many of the other instructional videos on youtube, you do not ramble about this, that or the other thing. You don't offer superfluous information about the job. you are direct and to the point.

[youngseanconnery]

You have saved people countless dollars with your well-done videos. Thank you Sir!

[caddy]

Very well illustrated. I am a retired electrical engineer & that is exactly how you should test a relay. Well done....

[eloctocs]

Thanks Eric. I just changed a bad relay for a buddies cooling fan and tested by swapping with another relay. I get home and you have this new video up. Perfect timing I did wonder how they work. Thanks again for you information. You really do help

[jonnyboat]

This is the best video I have ever seen to clearly and effectively explain how a relay works and how to test it.

[joc]

As an electrical engineer who happens to really like car stuff...I approve! Great video! As long as you know some basics like this, electricity isn't all that bad. Like you said in your last video, it works a lot like water.

[mike]

Thanks Eric, you, as always, explain things in a simplifed, "dumbed down" (Thank God) manner that I find very helpful and informative. Please keep it up!

[robertbaumann]

Yo Eric the car guy,
Thank you for your channel and the education I and others received on relays!!!! Means a
lot to people like me who need to repair their vehicles. God bless you for that!!!

[davidturner]

I followed you directions on how to check if there is a draw on a car battery. I purchased a digital multimeter and hooked it up like you said. I found there is a 1.42 amp draw on the system. Now I am going to go through the fuses like you said. I never even knew about relays before. Very interesting.

[prayfortruejustice]

Great video. Thanks Eric. One other issue you might cover regarding relays in older automobiles is the solder points. For example: older Acuras and and Hondas can have an intermittent relay problem (probably other makes as well), where the car wont start when raining or in the morning when its cold, or if there is dew because the relay solder points are "micro" cracked. The relay may pass the bench test in a heated garage, but wont pass if damp. Google: "How to solder and fix the Main Relay."

[stuzman]

Good point about the diode across the coil. One thing to keep in mind is that OE relay coils driven from the PCM usually have the diode across the coil to protect the driver. Cheap universal relays sometimes doesn't have this diode and could take out your driver because of the high voltage spike. Just something to keep in mind.

[davidstock]

Received 0.02 milliamps within parasitic engine off DC voltage draw, thanks to Eric. He isn't a gimmick, Eric has extraordinary experience.

[mp-wqsu]

Awesome Eric! Unfortunately I cannot do much of the sophisticated complicated heavy duty auto work anymore because I'm disabled with (MS). Your tips on at least me doing surface issues are definitely fulfilling! For the other issues at least good knowledge, when and if I need to take my car to a shop at least gives me money savings heads up on making sure I'm not going to get scammed, thank you so much!

[popxkorn]

Great video as always. Just a note that the diagram at the top of the relay is when it is at rest (off). I might add that I've seen relays be intermittent, so it may be useful to click the power on the low-power control-side about 10-15 times to see if it ever fails once. If it does, replace it. Also, ESI makes a relay tester (model # ESI-190) for those who need to test relays often.

[deathallfalse]

hi eric my name is logan i just wanted to thank you for all that you do to help us out im a student at ptec in florida and im studying automotive service technology there and watching your vids has helped me out alot and helped me get a firmer grasp on what im being taught so again thank you very much if you ever need something built for you shop be it shelving or what have you let me know and ill see what i can do hope you have a good day man PLEASE THUMBS UP SO HE CAN SEE THIS

[rwbishop]

Yes, making/breaking higher amperage circuits with the probe tip will greatly increase switch life! Doing so is a good habit to get into!

Most of (but not all) Power Probe 3's have an easily replaceable snap in switch. It's a good idea to keep a few spares on hand. The switch assembly is Power Probe's "Achilles' heel"

Older Power Probes, and early PP 3's have soldered in switches that are a PITA to replace.