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wiring "generic" plow lights

Discussion in 'Ram Trucks' started by 00 Ram, Feb 27, 2006.

  1. 00 Ram

    00 Ram Senior Member
    Messages: 113

    bought some generic plow lights...trying to get them wired up w/ the double-pole, double-throw switch in the cab so that I can select either truck lights or plow lights. But I think the switched ground setup in the 00 ram has me confounded.

    first, I'm not sure what's what on the vehicle's headlight power plug. (I can't be too far off, because after all is said and done, the truck's lights still work the way they're supposed to). on the 3 terminals (I'll call them "A, B, and C"), I see that A and C are hot when the headlights are on lowbeam. when I switch to highbeam, only C is hot. B is never hot. A and C are hot, even when the truck is off, and the key is removed.

    What I did was unplug the vehicle lights on both sides; on the driver's side, I re-routed the "+" wires to the DPDT switch in the cab; from there, I ran power to the plow lights, and to new plugs for the truck lights. The ground on the vehicle's original harness is tied to the ground on both of the new headlight plugs, as well as the ground wires for the plow lights.

    the park/turn lights are run in parallel to the truck's lights...simple splices join them together plow and vehicle park/turn lamsp are supposed to be on in unison.

    I ran all the wiring into a 6-pole trailer plug, so I can plug in the plow at a single point.

    problem: whenever the truck is plugged in to the plow, the parking lights on both plow and truck come on..even with the truck off, switch off, and key out of the ignition. :dizzy:

    I suspect that the "ever-present" 12v from the headlight circuits is somehow bleeding over to the parking lights circuit in the plow light, where it is feeding back to the truck's parking lights, and finding the ground there. I don't know why its doing this, as the plow light fixtures have a seperate wire for the parking lights and the headlights...but this is one explanation. so, how do I fix this?

    (plow lights have 5 wires coming out of their housings: highbeam/lowbeam/park/turn/ground. wires from each light housing are spliced together, except for the turns.)

  2. justme-

    justme- 2000 Club Member
    Messages: 2,138

    Firstly, you're going to start a fire if you wired it the way I read it. The power to the headlights shout NEVER be cut or splced to anything. The switch you are trying to wire in should be controlling a relay that switches the ground from the truck headlights to the plow headlights. NEVER switch in a high current application and you never want high current running in wires any longer than necessary because that causes more resistance and in the case of lights reduced light output.

    The parking lights are on because they are getting ground from somewhere else.

    The explanation of the terminals tells you that C is low beam +, A is high beam + and B is ground.
    when I only plug in the control plug in my MM1 there is no wire connected ground, only positive. My headlights on the truck go off and only the marker lights on the truck and plow light. The problem is No ground. When the power connecter is plugged in giving ground they work properly.

    That's all I can tell you without looking at the wiring. I'll see if I can locate a Shop manual for the truck and check the diagrams. Repair the wires you cut/spliced properly and get a relay for the circuit.
  3. 00 Ram

    00 Ram Senior Member
    Messages: 113

    well, I didn't cut/splice the headlight wires; I unplugged the factory harness from the headlights, and plugged it in to my own harness, which routes the 12v through a selector switch in the cab...only thing "spliced" is the parking lights. this used to be a standard practice. I think my problem is that I mis-read the pinouts on the factory harness, and the combination of reading "through" filaments, and the switched ground got me all buggered up. Had to put it on hold for a week, as I'm now in sunny FL, where snow is not an issue. prsport Hopefully, next week, it won't be -20 windchill when I'm trying to straighten this out.
  4. justme-

    justme- 2000 Club Member
    Messages: 2,138

    Probabily is simply misreading the pinouts. You deffinatly want to run a relay instead of putting the full headlight voltage through the cab switch. It was common practice, but so was plow truck fires...

    We have a factory manual in stock, I'll "borrow" it over the weekend and see if I can trace what wires you need by color.

    CARDOCTOR PlowSite.com Addict
    Messages: 1,304

    what i did was run my plow lights thru my fog light switch. with a relay
    the fog light switch is used to excite the relay. it works .this is my 2nd dodge ive done this too makes a clean install

  6. stcroixjoe

    stcroixjoe Senior Member
    Messages: 263

    I just hooked up saber light in a generic way i cut the connectors hooked up a trailer plug one for high and one for low put in line fuses in and ran 2 toggle switches it works good so far
  7. 00 Ram

    00 Ram Senior Member
    Messages: 113

    well, back from sunny FL. had a crack at the lights again this weekend, and found that I had in fact wired the lights correctly, at least in terms of identifying the pin-outs. I took apart the plow light fixtures to see what was going on inside there, and I found that the ground wire for the sealed beam headlights is tied into the park/turn fixture. So I cut that wire, and now the parking lights don't come on unless I actually TURN them on. ok...thats a step in the right direction.

    However...now the turn filament in the double-filament bulb doesn't function. when the turn indicator is activated, the park light filament blinks, instead of the turn filament. :dizzy: I found that re-connecting the ground line fixes this problem. So, I determined that what I need is a seperate ground line for the park/turn fixture. It wants a regular-old chassis ground, as do the park/turn lights in the truck, while the headlights work on a switched ground. So I ran another wire, and now, everything works the way its supposed to....almost.

    The only issue is that when I have the plow lights selected, the high-beam indicator is always on; dimly when I have low-beam selected, and brightly when I have high-beam selected. so something must be feeding back, I assume because the ground wires for all 4 headlights are tied together. Not sure if this is merely a cosmetic issue, or what. Seems that the solution would be to have a "triple pole/double throw" switch, but I don't think there is any such thing.

    the other solutions offered, involving relays and such: well, I've considered it, but I can't see any way to get this to work the way I want it to. seems to me that these solutions would only allow the use of low beams on the plow, or have both truck lights AND plow lights on at the same time, which isn't a good thing for a couple of reasons.
  8. justme-

    justme- 2000 Club Member
    Messages: 2,138

    the problem with the directionals and the ground wire: cutting the wire is telling you the problem is a ground is missing, cutting THAT ground wire and adding another for the direction is temporarily functional, but improper. find the ground issue and fix it there. The high beam indicator is another symptom of the ground problem. Lights that com on when they're not supposed to are usually a sign of a ground problem.

    Trust me you want to do this right, there's nothing worse than buying a truck someone has hacked and mickey moused the electricals on. And mechanics and dealers will triple the bill because of having to fix incorrectly wired things while diagnosing and repairing other problems.

    Let's go to the basics:
    What plow do you have on this? What was wrong with the original lights to make you change them?
  9. 00 Ram

    00 Ram Senior Member
    Messages: 113

    of course, the ground is missing. that's because the headlight switch interupts/connects the ground side on this year/model truck. unlike the more conventional method of switching the hot side. However, the parking light circuit's switch is on the 12v side, with a regular old chassis ground. There is only one ground wire going into the plow light fixture; If I connect that to the truck's chassis ground, the plow headlights will always be on, regardless of the headlight switch position, because the 12v is always there, regardless of the headlight switch position. So the plowlight's ground wire has to be tied into the same wire that the truck's headlights are tied to....but then, the park/turn lights have no ground...or an "inappropriate" one.

    well, that's exactly why I've done it the way I have, which I wouldn't charactarize as "mickey-moused" or "hacked". I made a seperate harness that simply plugs into the stock factory harness; to put it back the way it was simply requires that I unplug the factory headlight plugs from my harness, and plug them back into the truck's headlights. "plug-n-play", you might say.

    it is a snowbear plow. they don't come with lights. well...they have an "offroad light kit", which is by all descriptions...crappy. (But even if one were to use this system, it just attaches directly to the battery on the truck...2 lightbulbs and a fuse holder. no high/low beam, no turn signals...not road legal. point being: there is no factory harness for me to have "changed"). So I just bought the light supports that come with that kit, so I could attach "real" headlight fixtures.
  10. justme-

    justme- 2000 Club Member
    Messages: 2,138

    ok, so there was no existing plow light harness.
    They have used switched ground on most circuits for longer than I remember on all cars. Why switch the hot lead when it means you have to run more wire- just run a ground to the switch and a short wire TO ground from the switch instead of running 2 hot wires to a switch. easier wiring, more coes effective, more effecient.

    I worry about cutting into ground wires and such... I have had my share of repairing electrical work from others, includeing a Bronco I owned that had a fire in the dash while I was driving from someone wiring up trailer lights and a controller wrong.

    let me think on that a day or so, there's a simple solution-