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Relay Blues

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by 02HD2500, Mar 19, 2009.

  1. 02HD2500

    02HD2500 New Member

    relay wiring diagram needed. I've searched different sites but when i wire the relay up according to the diagrams it dosn't work how its suppose to. Maybe it could just be the type of relay im using. its a conduct-tite 30amp 12v relay i got at auto zone. Im wiring up the factory fog lights that my truck didn't come with. i'm using a toggle switch for the switched power source, and the toggle is getting its power from the fuse panel.
  2. 1st Synthetics

    1st Synthetics Epic Member 5+ Years 1000 Posts

    What do you need the relay for? Are your lights 12VDC? How many amps are the light[​IMG]s?
    Last edited: Mar 19, 2009
  3. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    My first thought, where it sounds like you just bought a generic relay, is if the relay is normally open or normally closed. what do you mean by, "the relay isn't working right?"
  4. 02HD2500

    02HD2500 New Member

    the switched source will run the lights with the constant un hooked.
  5. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    I have to apologize, as I'm not familiar with the proper terms (constant, switched) for relays, so I'm not 100% certain what you are referring to (though I would love to be educated). Gut feel is that you've got a normally closed relay, and you really wanted a normally open.
  6. Chris Miller

    Chris Miller Rockstar 100 Posts

    If I'm not mistaken, the part you're looking for is a Duralast # MR78.
    You'd be better off with a Borg-Warner relay from Advance, though.
  7. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Most generic relays can be switched on and off with either power or ground. It all has to do with how you wire it up. If you Google it you will find a wiring diagram that shows the various pins. They should be numbered 30, 85, 86, 87. Most relays use these numbers but some do not.
  8. 02HD2500

    02HD2500 New Member

    yes it has those #'s on it . i think maybe i just got a bad one or the wronge type.
  9. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    30 is always B+ and goes to the battery. You should have a fuse in this line between the battery and relay.
    87 is always the load or in this case the fog lights.
    85 is the ground wire. You can trigger the relay with this ground if 86 has battery voltage.
    86 is the voltage wire. You can trigger the relay with this wire if 85 is grounded.

  10. 02HD2500

    02HD2500 New Member


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