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wiring in fog lights????

Discussion in 'Chevy Tahoe Forum (GMC Yukon, Cadillac Escalade)' started by twiggy, May 16, 2009.

  1. twiggy

    twiggy Member

    I've got two fog light's mounted on my grill gaurd. i'm not that good with electricity so this might be a stupid question, but anyway i've got them wired together and then to the bright light on my left headlight. and i've got a 15amp fuse between the bright lights on the truck and the fog lights. everytime i put in a fuse, it just blows after a couple minutes of running them. Is the fuse just to small? Am i doing something wrong? should i wire one fog light to the right side and one to the left? any help would be greatley appreciated!!

    Thanks in advance
    -Jason

    Attached Files:

  2. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    What is the wattage on the fog lights?
  3. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Here is the basic formula to figure out how many amps you are pulling:


    Watts/Volts = Amps


    So if you have 55w fog lights it would be:

    110w / 12v = 9.16 or 10amp



    I would advise you, at the VERY least, split the two fog lights to the two high beams. The thing is that you're still using the same amount of power from the headlight system.

    The TRUE way to hook up what you are trying to do is with the use of a relay. A relay is a low-powered *switch*, in essence. It is used to provide high-powered accessories power by using a low-power system to activate it --- if that makes any sense to you!

    It has been mentioned many times on this site but here is the way you want to set up your relay, bought at any auto parts store and most hardware store.

    The relay you will need will only have to have 4 terminals, though a 5th terminal might be present. The 5th one you just won't use.

    Near the terminals (or on the diagram of the relay) you will notice a number. To the best of my knowledge all the numbers are always the same.

    Here is what you'll need and what you need to run where:

    Relay
    Fuse holder (an additional one)
    Length of 12g wire (about 20 feet or so)
    4 female spade connectors
    1 jumper connector (clips onto a wire and allows a second wire to get power from the one it's clipped to)

    Here's what you do:

    Ground both fog lights (already done for you, I think)
    Bring the two (+)positive leads from your fog lights together and run a length of wire from then to the relay
    The wire gets a female spade connector and gets pushed onto the terminal of the relay with the number 87
    Run a ground wire from the truck to the relay
    The wire gets a female spade connector and gets pushed onto the terminal of the relay with the number 86
    Jump a length of wire to one of the (+)power wires of a headlight and run it to the relay.
    The wire gets a female spade connector and gets pushed onto the terminal of the relay with the number 85
    ***closer to the headlight cut the wire you just put on and put in a fuse of low rating - 5amp or even 2.5 should do***
    Last wire gets run from the (+)positive side of the battery to the relay
    The wire gets a female spade connector and gets pushed onto the terminal of the relay with the number 30
    ***closer to the battery cut the wire you just put on andd put in a fuse of a rating that coincides with the wattage of your fog lights (added together!)***

    That's it! Just screw or bolt your relay out of the way and out of the elements and you're done.

    Essentially what happens is....

    Power is supplied to the relay via the wire that goes from the battery to terminal #30.

    The 'switch' is operated by your highbeams. Once you turn on your lights it will supply power to the (+) wire, get sent to the wire you spliced in which goes to the relay (terminal #85).

    The circuit there is completed, with terminal #86 being grounded, and so the 'switch' is turned on.

    Now THAT circuit is completed, with terminal #87 getting powered by the battery which provides power to the foglights, which are grounded on the other end.
  4. twiggy

    twiggy Member

    thank you so much for the help, i'm gonna try doing all that tomarrow. I really appreciate it man. i am really bad with electricity.....
  5. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Well, this is a really easy first start. Just remember to do the battery lead/wire last and cut a fuse into it before doing anything like trying the lights. At worse you should just fry the fuse(s).
    1 person likes this.
  6. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts Platinum Contributor

    Alright I printed out your post Springthing, I am such a moron when it comes to relays. I try to read schematics, but I am kind of brain dead when it comes to relays. Thanks for the great info, see I learn something new everyday on this site! :party:
  7. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    I'm going to have to hand-drawn easy schematics and instructions on how to do the relay thing. It comes up every once in a while and easier to do than most people think.
  8. twiggy

    twiggy Member

    I found this schematic, and it seems to match you descripiton

    [​IMG]
  9. Grizzly Guy

    Grizzly Guy Rockstar 100 Posts

    excellent schamatic,even I can understand it,,thanks
  10. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Yep, that's almost exactly it only instead of using that switch, you are using the power from the high beams in your case.

    I would add the fuse between the ignition or whatever (+)positive power is used and the switch because that, in essence, is a separate circuit and it is not fused in the schematic shown. (in your case it's the fuse between the relay and the headlight (+)power wire.

    Also, for those that may use the above, please note that the indicator light will turn on when the SWITCH turns out. So... just because the light on your dash lights up doesn't mean your fog lights are actually working. You could have a blown fuse, fried relay,bad grounds or dead bulbs and the indicator light will still come on. Thought I'd mention that.

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