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Running 2 55W lights....what amp fuse and how to run a relay (needed?)

Discussion in 'The Garage' started by zakk, May 13, 2003.

  1. zakk

    zakk 1/2 ton status

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    I picked up 6 lights this past week. I want to run two lights to each switch. I was thinking of wiring them to the + terminal on the Starter, then to a relay, , then to a fuse, then to each switch.

    will this work? this is my first major undertaking with aftermarket electrical work.

    TIA /forums/images/graemlins/cool.gif
     
  2. scrappy88

    scrappy88 1/2 ton status

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    A relay technically isn't required but it's better to use one. Typically you'd have a +12v line going from the battery to one side of the relay, and the other side of the relay hooked to your lights. Put a 15 amp inline fuse in between the relay and battery. For powering the relay coil, wire your switch to it from somewhere in the cab (I usually just tap into one of the acc slots on the fusebox). Fuse that line as well just to be safe (1 amp fuse is fine). Ground the other side of the relay coil, and ground your lights and you should be set. /forums/images/graemlins/thumb.gif
     
  3. Hossbaby50

    Hossbaby50 3/4 ton status

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    Not to post jack, but what would be different for 130watt lights? I just picked up 2 the other day and I need to wire them up.
     
  4. scrappy88

    scrappy88 1/2 ton status

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    Zakk here's a cheap diagram of how I usually wire stuff with relays:

    [​IMG]

    It's a Bosch style automotive relay, but most automotive relays are similar to that.
     
  5. scrappy88

    scrappy88 1/2 ton status

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    A pair of 130's would pull around 22 amps, so a 25-30 amp fuse would be fine, and use 10 gauge wire. /forums/images/graemlins/cool.gif
     
  6. Thunder

    Thunder 3/4 ton status

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    To figger amperage(fuse size) divide total watts in the circut by volts
    ex: for two 130 watt lights:
    130x2= 260 total watts. Divided by 12 volts = 21.6 amps
    Use at least 25 amp fuse to be safe.But dont use a higher fuse than the wireing is rated for. #10 wire is rated for 30 amps.
     
  7. zakk

    zakk 1/2 ton status

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    scrappy,

    what size fuse would go in between the Acc/Fuse Box and the in cab switch? anotehr 15amp? (110W/12V = ~15 Amp Fuse)
     
  8. bobsurf

    bobsurf 1/2 ton status

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    As always, thanks for the information guys. Seeing that I knew nothing about relays (and how they work), I did some research via my buddy google. I found this cool article on Relays and thought I'd share.

    RELAY ARTICLE

    Happy Hump Day.
     
  9. scrappy88

    scrappy88 1/2 ton status

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    The relays only pull about 0.1 amps, so a 1 amp fuse would be fine along with #16 wire. That portion of the relay circuit only powers the little magnetic coil in the relay. The high-current circuit that powers the lights is electrically separate from the low current circuit that powers the relay, which is nice because you don't need to run high-current wiring inside the cab. /forums/images/graemlins/thumb.gif
     
  10. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    The in cab circuit just trips the relay, very low amperage draw. As suggested earlier, a 1 amp should be enough, but check the amperage draw on your relay...
     
  11. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hehe, that'll teach me not to open a couple of windows and get distracted... /forums/images/graemlins/ignore.gif
     

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