75 SR5 - Relay (Headlight ) - How To Test if Good/Bad w/MultiMeter?

Discussion in 'Interior/Electronics' started by Busted Knuckles, Jul 5, 2015.

  1. Busted Knuckles

    Busted Knuckles Member

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    My headlights went out.

    One evening, I was driving into a parking lot, went thru a dip in the road, and my headlights went out.

    Took out the relay and sanded down the metal connector and the area the relay bolts into for a good connection/ground. Still nothing.

    How is a relay tested?
     
  2. aaron_sk

    aaron_sk Enthusiast

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    Load the coil with a battery and check for a closed circuit between the common and switched terminal.

    Or bin it and replace it with a cheap, reliable Bosch.
     
  3. tyrap26

    tyrap26 Enthusiast

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    before replacing anything do you have 12v at the light?
    do you have a wiring diagram?
     
  4. Busted Knuckles

    Busted Knuckles Member

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    I've check with local auto part stores. None can find a replacement in their sources/suppliers.

    Went to local Toyota dealer: $60 and must be ordered from Japan!

    So where do I get this Bosch???
     
  5. Busted Knuckles

    Busted Knuckles Member

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    Yes, I have a wiring diagram Haynes Manual).
    I think I checked the for 12v awhile ago .... before headgasket issue...
    Will check again.

    Should I check all the fuses and wires for breaks first?
    ( I'm told relays don't go out often, just reset...)
     
  6. Mikerocosms

    Mikerocosms Veteran

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    How many pins does your relay have? Typical is either 5pin or 4 pin. You can always get them from amazon. I buy these and they have worked well for me.

    5pin relays




    .
     
  7. jetas

    jetas Grand Toyotaholic

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    The factory relays only have 3 pins dont they?
     
  8. tyrap26

    tyrap26 Enthusiast

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    Yes you should always start with your basics, therefor fuses.. If you have 12v at fuses then continue on to wires leading to relay.. so on so forth. relays do not fail often but with the age of your truck its possible. Just follow your diagram and remind yourself to stick to basics before digging deep. Electrical is intimidating be very simple.
     
  9. aaron_sk

    aaron_sk Enthusiast

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    Three pin relays have one side of the coil closed to the common, or possibly grounded to the case. Your wiring diagram will show you how the relay operates and it will be obvious how to replace it with a four or five-pin.

    I would confirm 12V at the light first. Confirmed there, check the ground, failing there confirm 12V at the relay. Confirmed there test the relay, failing there check the fuse.
     
  10. Busted Knuckles

    Busted Knuckles Member

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    Once again, I did a little from everyone.
    And it worked!

    I checked 12 volts at fuse box: 12 volts.
    Checked 12 volts at female three pin: 12 volts.

    Cleaned both male and female parts with electrical cleaner.
    Then roughed the the three spade relay metal bottom with sand paper and cleaned for good connection.

    Sanded down connection area in engine body and cleaned for strong connection.
    Bolted in with resistor.

    Lights - both high and low beams -- work!

    Not sure why. Same relay...
    But I'll take it!
     

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  11. jetas

    jetas Grand Toyotaholic

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    40 years of the elements starts corroding things. Corrosion breaks electrical contact
     

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