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Wiring plow lights hi/low beam with relays

Discussion in 'Truck & Equipment Repair' started by Charlie'sChaps, Dec 2, 2012.

  1. Charlie'sChaps

    Charlie'sChaps Junior Member
    Messages: 10

    Hi,

    I am in the process of wiring plow lights with relays. The kit I got with my plow is the old style DPDT switch you are suppose to tap off the floor switch for hi/low beams. Needless to say, I don't want to go that route.

    This is the diagram I want to follow but have a question.

    I see that you tap off the existing bulb connector and wire the relays and the plow lights. Now my question is where do you attach the leads from 87A that go back to the vehicle headlights (high/low) Do these run back to the lights downstream from where I made the initial tap?

    Any suggestions would be great.

    Thanks.

    plow light wiring.jpg
     
  2. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,973

    the leads ftom 87a goto the light themselfs. your gunna have to take off the factory headlight connector, and install another one,
    and as far as i see it, you have 2 options.
    1) use only the 4 relays for both lights
    2) use 8 relays, 4 for each side.
    and just fyi theres some places tha sell the male end of the headlight connector, depending which ones you have
     
  3. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    Your diagram seems a bit heavy on the relays, light on the actual necessities.

    First off, your truck already has relays for the headlights, both high and low beams. There is no sense in duplicating them. In other words, your two SPST relays are redundant.

    What I would do, is determine how many circuits the truck has for running the headlights. Some vehicles run only a SINGLE circuit to power BOTH low beams, and a second SINGLE circuit to power BOTH high beams. Other vehicles use four separate circuits to run left, right, low and high beams. You can find the number of circuits by checking the number of headlight relays your vehicle has, and how many outputs each relay has. If it has just ONE SPDT relay, it is a TWO circuit system, one for high, and one for low. If it has a DPDT relay, or two SPDT relays, it is a FOUR circuit system.

    In a TWO circuit system, you need a total of TWO SPDT relays. In a FOUR circuit system, you need FOUR SPDT relays.

    Wire it like this;
    Find a SWITCHED POSITIVE source, i.e., one that is ON or OFF with the ignition switch. This is important because you don't want to drain the battery by leaving the system on "plow lights". Wire your truck/plow SPST switch into the coils, other side of the coils to ground. SOURCE wire to common connector on the relays, NORMALLY CONNECTED (NC) to TRUCK lights, NORMALLY OPEN (NO) to PLOW lights.

    So what this will do, is switch the switch the power from truck to plow lights when the switch is turned ON.


    Now if you want to get FANCY with this, get yourself a couple of DIODES. They each need to individually be able to withstand the voltage and current required to power the RELAYS. Wire the positive sides of the two diodes each into a source HIGH, and a source LOW (it doesn't matter if your truck is a 2 circuit or a 4 circuit, just pick ONE low and ONE high circuit). Connect the negative sides together and use THAT as the power source for your truck/plow switch. Now the relays will be powered any time the lights are turned ON AND the switch is turned to the "plow" side.

    A diode is basically a one-way-valve for electrons. Wired like this, they basically form an "OR" circuit, without letting the two circuits bleed into each other. It provides power to the "system" if your low beams are on **OR** if your high beams are on.

    Your logic equation would be like this;

    (HIGH OR LOW) AND (PLOW) = POWER_RELAYS
     
  4. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Of all the projects I should have taken pics of........

    Jason,

    How do you know his truck already has relays for the headlights?
     
  5. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    Simple: because it takes a BIG FRIKKING CLICKER to handle 8.3 amps (2x60 watt bulbs = 120 watts, divided by 14.5 volts = 8.3 amps) reliably over long term use. Dashboard level switches are universally LOW current switches. Relays are under the hood to run things like headlights. The low current switch will activate the high current relay.

    Alternatively, maybe he drives a truck made in the 50's that HAS a BIG FRIKKING CLICKER of a headlight switch.

    Either way, there is no reason to add another relay.
     
  6. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Hey, thanks for making it really clear to the rest of us just how much you know about vehicle electrics....saved me some work.
     
  7. Holland

    Holland Senior Member
    Messages: 605

    Duh, all you need is scotch locks and electrical tape. :dizzy:
     
  8. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,973

    Why even bother with the tape. Scotch locks are the only way to go :)
     
  9. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    One or the other is all you need. One or the other
     
  10. Holland

    Holland Senior Member
    Messages: 605

    well, "technically" you could do it that way.. but its best to do it the PROSELFINAL way
     
  11. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,973

    Yea. Scotch locks. Ok I can't even say that with any honesty
    There's no technically. It shouldn't be done that way !!
     
  12. Holland

    Holland Senior Member
    Messages: 605

    Hey now! Theres a place for them... the trash! Thumbs Up
     
  13. basher

    basher PlowSite Fanatic
    from 19707
    Messages: 8,992

    If you are going to build your own harness buy a set of one of the manufacturer's headlight adapters for your truck so you can use the headlight plugs instead of cutting the harness. It will also assure you get the right wires.
     
  14. Charlie'sChaps

    Charlie'sChaps Junior Member
    Messages: 10

    It's a 07 F150. I want to use the headlights as well as the plow lights and switch between them.

    I like the idea of using some headlight adapters.

    The wiring that came with my plow lights is seriously lacking. I do not like it at all. I don't want to go from the trailer plug, seems foolish to me.

    I will have to look around a little more. I am mechanically inclined, just not in advanced electronics :) And yes, multiple relays etc. to me is advanced electronics LOL.

    Thanks guys.
     
  15. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Not on an 07 F150, only one headlamp relay on those. And it isn't under the hood.


    Again, not on an 07 F150. There is no low beam relay. Lows are powered directly through the big frikking clicker...as you gallantly put it. .
     
  16. Charlie'sChaps

    Charlie'sChaps Junior Member
    Messages: 10

    OK. So if I may bother, what is the best way to wire these plow lights in conjunction with the existing lights? I could just tap into the fog lights to get low beam plow lights but I want to get the deluxe package. :)

    Thanks.

    Charlie.
     
  17. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,973

    Just get 2 flashlights ans duct tape them to the plow. There done,,and no wiring involved. Bahaha. Lol
     
  18. Charlie'sChaps

    Charlie'sChaps Junior Member
    Messages: 10

    I'm Canadian, I will use hockey tape!
     
  19. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,973

    Ok sorry for the mix up. Eh! Lol
     
  20. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,973

    Do you want the easy way to do this ?? Switch, relay, wiring spst switch.(2 or 3 pin switch). Get hot wire from an ign source, to switch. Out to relay...one lead off battery, and gnd. Last lead out to the plow lights. Nice and easyinstall, no heavy wires in cab,,,and the plus of only plowing with your headlights on and nothing else