How to Test a Relay the Correct Way

Here is how you test a car relay the correct way. Really the one and only way it should be tested.

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[robertclymer]

I know this video is like 8 yrs old, but I am so glad it is still up. Yesterday at the car show, a fan came up just after I pulled in and parked. He was sharp. He noticed right away one of my dual elect. radiator cooling fans was not working. It has a built 460 in the 67 Mustang and it has been running hot.(It is also very hot outside too). I planned on putting a toggle switch in anyway so I can turn them on earlier rather then when it is 185 deg or higher. Wired up the toggle switch, and test both relays for the click. Will finish up with the resistance check tomorrow. Thanks so much for sharing this info. It has helped so much. Cheers from Motown.

[jtwitch]

This is one of the most well laid out and simple to understand vids on relays. Thanks for not making it to complicated.

[robertdangerpaulson]

A couple basic tips for those who don't know: A normal switch has 2 basic states, normally open (NO) or normally closed (NC). When power is sent to a switch it change states, so a NO switch will become closed. That means power will be distributed to any legs designated after the switch. A NC switch does the opposite, when signal power goes to the switch it will open the circuits, terminating power distribution.

Troubleshooting note: A digital multimeter had two fuses. One for checking voltage, and one for checking continuity. ALWAYS check voltage before checking for continuity. When checking for resistance the meter uses its own power to test the circuit. If there is voltage on the circuit it will automatically blow the fuse because you're checking resistance on a hot circuit. Check voltage before resistance and you'll never need to replace fuses or worry about testing a hot circuit

[kevinmullins]

For all the questions about "Make sure the ground is connected to ground and the power goes to power, " ...

Typically-
pin 85 is ground (negative)
pin 86 is power (positive)
pin 30 is constant supply power to whatever is being activated by the relay
pin 87 is the output of pin 30 when it gets switched on. 30-->87

To be certain which pin (85 or 86) is positive or negative...the diagrams often have a symbol of a diode (triangle and a line) on either pin 85 or 86, whichever pin the "line" side of the diode symbol goes to is negative.
Connecting power backwards will simply do nothing, this is what the diode does.

[hgf]

Best video on relays I have seen so far, simple, well explained and easy to follow for complete beginners like me. Well done!

[Al_Bundy_]

Watched a couple of videos for testing relays and this was the most direct approach and easy to follow.Thanks.

[henrikbreum]

Very good info for us who are "challenged" when it comes to electricalal tasks. Thank you.

[mauriceshumock]

Ratchets and wrenches, love your videos. I just wanted to add one thing you forgot to mention. 95 percent of the time a resistance or continuity check is perfectly fine but sometimes a bad switch will show good resistance but as soon as you load it with more current than what the multimeter can put out it will go back to an open circuit. This concept burned me a couple times before I understood it and will make you go crazy if you aren’t aware.

[ScotDavids]

Excellent video. You have a natural talent for instructing people about technical things. This really helps me.

[hectormontesdeoca]

WOW, thank you for putting together such a good lesson. Straight forward, and will really help me confirm if I need a replacement relay for my fan. You are doing good for the little people! Thanks again!

[robertcrislip]

really good presentation of how to get power for bench testing. and explaining the diff between good and bad parts i have seen the half hazard testing. kudos

[DIYCarRepairGuy]

This video is great. I tried each step and it worked smooth.
Straight to the point and informative!

[rorywynhoff]

The flapper is called a contact.
Thank you for the videos!
Love your channel ❤️

[leodentperu]

Your explanation was simply the best one! I made me remember my school class about sensors and switches. Thank you so much for your video material.

[rayyman]

I have been watching DIY car repair videos on You Tube for awhile and you have some of the easiest, most useful, and simply best videos out there thanks.

[jorgeperez]

You are by far the best teacher on youtube when it comes to cars!! Very insightful and easy to understand. Thank you so much ratchets and wrenches love your work!!!

[poponachtschnecke]

The flapper is a switch...one of the few things I learned in college. I love the footprint on the floor.

[markh]

Thank you . I have a CEN-TEC relay tester tool that does both the switching test and the continuity test at once BUT until I saw your video I didn't fully understand it was doing that. Just toggling mode 1 and mode 2 on tool and matching readout to answer in booklet. So I am like a kid with a calculator that didn't learn to add. Thanks for teaching .

[duanebonney]

Thanks to you, I found my problem so much quicker. Relay was clicking, but no resistance. Much appreciated.

[ricewinner]

Good video on continuing to verify that that flapper, normally opened: bridge, switch, etc. has the continued loop for that circuit.👍