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Thread: back up light

  1. #21


    Glad to see that you got it working, however, the reverse light circuit is not designed to carry that type of current. Not trying to beat a dead horse here, but you really do need to put a relay in for that. Just go to the zone and ask the guy behind the counter for an off road light relay. Here is a link to one:

    What a relay does is allow you to use a low current wire to switch a high current device. A relay is nothing more than an electronic switch. When you feed 12 volts to the coil, it closes contacts that are rated for much higher current to feed high current devices like off road lights. While you can safely power a relay with your reverse light wire, your tail light harness is designed to have a load of maybe 5 amps drawn from it. When you start trying to pull 10 to 15 amps through that wire, it will get hot and start to melt the plastic insulation. Eventually, it will melt into another wire and either cause a short or make really strange things happen. A fuse by itself is going to do nothing to stop you from melting your harness.

    Think of it like this... A fire hydrant is your battery. It can make LOTS of power. Think of the wire to the reverse light like a garden hose. It will do a good job at watering the lawn or washing the car. now hook one end of the hose to the fire hydrant and the other to a fire truck. Now, we know that the hydrant can supply all of the water the fire engine needs, but not through a small hose like that. The fire engine will suck the hose flat, causing the water to stop flowing, possibly damaging the pump on the engine and ruining the hose.

    Granted, the reverse lights are not going to spend a lot of time in use, but if you are going to take the time to do modifications like this one, you should at least take the time to do it right, rather than to come back here in 3 months asking why you keep popping fuses and see smoke coming out of the dash when you turn your lights on. a 7 dollar relay and 10 feet of wire is going to be a LOT cheaper today than replacing a wiring harness later.

    Just my .02 and worth every penny that was paid for it.
    Last edited by moogvo; 03-09-2012 at 10:57 AM.
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  2. #22


    Im going to order one from amazon. I understand the load problems I was just impatient with putting it on my one question is should I run the power lead to the battery for the relay

  3. #23


    Yes. And fuse it at the battery. Looks good btw. Why only one light instead of both? You might consider running a second wire to the relay so you can turn it on with a switch. Just use a diode to keep from sending power to the reverse lights when you turn it on. Really handy for coupling a trailer at night...
    Last edited by moogvo; 03-09-2012 at 11:11 AM.

  4. #24


    Ordered relays just now it's a 5u pack so I wont have to worry if I need another relay also ordered wire cuz gonna need more than just 10 feet and I really only wanted one light on that side.

  5. #25


    when i do my 55 watt driving lights later this spring should i also use a relay even thought it will be on its own independent switch and power lead. im just wondering while were already talking about it. also does any one have a wiring diagram for a on-off-on switch.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

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  6. #26


    Yes. Use a relay for any high current accessories. I am not sure what to tell you about a wiring diagram for an on off switch. You have one wire going in, one going out and sometimes a third connection for a ground.

    I am going to put relays on my headlights when I have a chance. Makes them brighter and last longer since they will burn at the correct voltage.

  7. #27


    ok i was just double checking then it deff a good thing i ordered the 5 pack of relays

    it deff gonna take more material but will be better in terms of simplifying how the wires run.

  8. #28

  9. #29
    Master Mechanic
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    Feb 2012
    New England


    Quote Originally Posted by Enkeiavalanche View Post
    I have the Whitenight backup lights. Easy plug into a 4 pin harness. It comes with a 3 way switch that allows you to turn it on from behind it or on when backing up. It has a relay inside too...
    I noticed that the spot on your bumper where the wiring plug is located, is filled in. Did you relocate the wiring down to the hitch?

  10. #30


    Quote Originally Posted by moogvo View Post
    What you need to do to do it "right" is to connect a RELAY to the reverse light in the tail light harness. Then run a heavier gauge wire from a higher amp rated fuse to actually power the light with... Otherwise, you can melt your taillight harness. It was not meant to provide the power needed for a 55 watt bulb.

    Otherwise, you might get undesired results...

    "I bought a new car once... and I got burned."

    wait is that ur aztek in the picture????

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