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Coolant Fan Switch Testing WITHOUT Removing From The Vehicle | How To Bypass Radiator Fan Switch

This is how you can test a radiator or coolant fan switch without removing the sensor from the vehicle. This will also show how you can bypass the switch entirely and turn on the cooling fans instantly.

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The coolant fan switch is sometimes referred as the following:
Radiator fan switch, engine cooling fan switch, fan thermostat temperature switch, thermo switch, thermo fan switch, fan control switch, coolant fan switch, thermostat temperature switch and water temperature switch.

Any attempt to repair automotive parts and/or systems carries risk of personal injury. Always adhere and follow safe practices when working on vehicles. Such as, safety glasses, jack stands, no loose clothing, etc. No guarantee or warranty is implied. Use the information in this video at your own risk. Carsntoys is a member of the Amazon Influencer Program.

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  1. Can I just say, the state of that engine bay and f20c is beautifully clean. I love the look of that enginee

  2. that quick bypass trick there would that also be viable to use say if your actual fan stopped circulating as you described. Now would a person be able to rig a set of wires as you did with the pin probes and got the fan to immediately come on. Without it running constantly while operating the vehicle ? meaning could it be set up to operate like a amp can be stilled used if fuse blew and you wrap a small amount of wire around the fuse and stick it back into the fuse location and it then returns power where it had previously blown leaving no power ? can radiator fans be done like that so they work but not work running constant?

  3. Great vid! Do you know where the cooling system temperature sender/sensor is located on a 1999 Oldsmobile Intrigue? The fans work and the fans’ relays are good but I can’t locate the cooling system temperature sender sensor to test it and replace it. Thanks.

  4. Greetings from England, near London. Thank you for explaining how to do this and you did it brilliantly (You have probably saved me a lot of money)! 🙂👍

  5. What if it’s a three prong how do you test that

  6. Thanks. I have an 87 Comanche 4.0 auto

  7. On my ‘05 Outback XT, when I turn on the A/C, the fans turn on high only, regardless of engine temperature and never come down to low speed.. everything else seems fine. Could this be a bad rad fan switch?

  8. I replaced my cooling sensor it worked for a few hours…
    Then the fan wouldn't turn off so I had to disconnect it manually.
    Now it's not kicking on at all…
    I checked the relay box and the cooling fan fuse has a bit of melted plastic on one of the prongs.
    I switch the fuses with one I had with the same voltage but the fan will not kick on…
    My fan is about a year old and it still works because I tested it with just the battery hooked up to it…
    Idk what the issue could be…

  9. Great diagnosis and explanation. Having same issue with my 97 BMW. Same concept, same idea but have a low and high speed setting. Will bypass today to test the fans, but most pretty certain its the switch that has gone bad.

  10. My fan is running as soon as I switch on the car while it's still cold

  11. thanks I have a Suburban 2012 and I want to make both fans works on high speed all time what I have to do should I remove only the black wire from radiator sensor .

  12. Thanks so much for sharing this valuable information…🙂
    Remember that God loves you, and wants you to love Him too 🙂

  13. Hi sir.I have problem while engine cold everything ok when engine hot fan work and non stop until i stop the engine.Radiator,fan,coolant,coolant cap changed with new one

  14. How do i get my fan to spin the other way? I have a mk3 golf and my connector has 3 of those metal things not 2 like yours

  15. only one of my fans turn on after this test said resistor bad its a 92 hyundai excel but cant find part anywhere'

  16. In my honda accord after ignition when I turn on AC, radiator fan runs for few second and then stop. Not getting clue where it's missing.

  17. Is that switch normally open ?

  18. FAN-tastic.was wondering how to test my motorcycle fan-YOU ARE GREAT!

  19. Hello, so mines is a 3 wired connections how would I know which 2 should I used to do the test?

  20. My radiator fans come on when I unplug the connector of the cooling fan switch AND go off when I short them like u did.
    Why is it the case.

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