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festerw said:


Pin 30 runs to a fused positive battery connection
Pin 86 runs to a ground
Pin 85 runs to the trigger (ie factory low beam wire or switch on dash for plow lights)
Pin 87 runs to the accessory you want (ie plow lights) and is normally open
Pin 87a runs to another accessory (ie headlights) and is normally closes

Pins 87 and 87a simplified: Pin 87 will have power when the plow light switch is on 87a will have power when it is off.

I have a diagram here somewhere if you want to do a headlight wiring upgrade too that will take pretty much all the load off of the factory headlight switch.
If you hook it up like this,the truck headlamps will remain on all the time,unless the relay is energized,then you will have plow lamps.

If you want it to just switch from truck lamps to plow lamps,you need to have the feed from the truck headlamp switch coming in on pin 30,and the relay needs to be triggered by a separate switch which flip between truck and plow lights.Youll need two relays to have the high beams switch too.

Pin 30 is the headlamp feed input
Pin 86 runs to a ground
Pin 85 runs to the trigger (ie factory low beam wire or switch on dash for plow lights)
Pin 87 to plow lights
Pin 87a to truck lights

If you want to isolate the headlamp switch,then you will need another relay or two,which supplies battery power to the relay(s) you installed to switch the plow lights,and is triggered by the headlamp switch.
 

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wyldman said:
If you want to isolate the headlamp switch,then you will need another relay or two,which supplies battery power to the relay(s) you installed to switch the plow lights,and is triggered by the headlamp switch.
I should have mentioned that, thanks for pointing that out.

And here's the diagram that I used, for mine I connected everything with 10 gauge wire except the triggers for the relays that I used 14 gauge. The switch is also powered by a ignition on source, not the battery (that was just easier to draw). I also used some 30 amp circuit breakers for the power to the relays.

 

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Think of relays like an electronicly controled switch. When you supply juice to the coil (85 or 85) it will close the switch. It needs to flow through the coil to ground(you can supply juice to either terminal as long as the other one is grounded). There is no real current flowing through this circut. You could wire your "trigger" wire to your coil with very small wire since there isnt any flow through it regardless what circut the trigger wire is hooked to.

The NO(normaly open) is normaly open(juice wont flow through it) unless the trigger wire or the coil is getting juice. Likewise the NC is normaly going to let juice flow through it unless there is juice to the coil.

The shorter span of wiring you can run thats actualy powering something(headlights or the like) the better. Also since the trigger wire for the coil isnt using any juice you can pretty much stick it on any circut and not worry about drawing too much through that circut. Then you can connect your normaly closed or open to what ever circut you just made and let the heavy current go through that.

Always use relays. Every switch in my truck does nothing more than power a relay. Means I can run most of my wiring as very thin wire....witch is easier to work with and cheaper. Plus it wont handle much current so it acts like a fues in itself since it will fry itself quickly if it shorts to ground. I also dont have big current carrying wires running through my dash.

Make sense?
 

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lights

i got real simple and made a plug on the markers and turns off from my trailer hitch .and then ran headlights back from the relays the proper way to the switch so that is controlled from the dimmer switch and the trucks relay system. so i cheated on the markers and turns so i didnt tap the wiring harness . that is really against my religion. but i will if i need to.:drinkup
 

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hootney said:
i got real simple and made a plug on the markers and turns off from my trailer hitch .and then ran headlights back from the relays the proper way to the switch so that is controlled from the dimmer switch and the trucks relay system. so i cheated on the markers and turns so i didnt tap the wiring harness . that is really against my religion. but i will if i need to.:drinkup
There really is no problem tapping into the markers\turn signals if your doing it right.If you solder and heatshrink,it's not a problem.Much more reliable than running off the trailer plug.

Some of the newer trucks will have problems when you tap into them,as they have computers that monitor the circuits,and don't like the added resistance of the plow markers and signals.Newer Dodges are one of them.You can isolate via relays,or just buy a relay kit for that purpose.Comes pretty much wired,you just connect the markers and signals,and run the power wires to the battery.
 

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Hey, Alan, can you direct me to the thread on how to wire plow lights with a double pole double throw switch? I just pulled a plow off an old truck and mounted it on a 1990 F150 and need to start from scratch with the wiring. Thanks!
 

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Due to the complexity of your trucks headlamp circuit,adding a simple toggle switch is no longer feasable.

Either you need to do it with multiple relays (like the plow mfg's do with their systems),or keep it simple and wire them separate.

If your going to wire them separately,then you can do it easily with just a switch to supply power to the lights.If you want high beams,you'll have to wire those up too.You will need to leave the truck lamps off,but keep the running lamps on.The plow markers\signals can be wired into the truck wiring so that they work in sync with the truck markers\signals.

They way I usually do it,is a little more complex.I use a relay to control the plow lights.The control side of the relay is powered from the running lights (as they will be turned on when plowing at night),and it is grounded via the plow grille connector.This way,the plow lights only come on when the plow is plugged in,and the running lights are on.It's a great way to retrofit a plow to a truck without having to buy the correct truckside wiring harness,associated relays,or a isolation module.The only drawback is no high beams,but nobody ever really uses them when plowing.if you want high beams,you will need to add a switch,and one more relay.

That is how I built my harness. Two relays, hi and low beam, and then all I did was tap off of the turn signal lights using heat shrink and solder. No wire taps for me. I also built my plow control harness. Pretty easy.
T.J.
 

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Anyone know if I could wire my plow lights up using a relay like described and tapping into the parking lights to use as the turn on? Truck is a 2003 Chevy 2500 HD...
You certainly could do that but i don't think you'd want to. Then your plow lights would go on whenever your parking lights were on. I would think that you would want to be able to switch between your plow lights and your regular headlights, right?

I just wired mine up the old fashioned way without relays. It took me a while and a bunch of reading to get my head around how to do it. After all my homework, I'll try to explain it as simply as I can. Bear in mind I've got a 1990 Ford F150 with a floor mounted hi/lo beam switch.

Let's start with the headlights because they are the semi-confusing part...
I bought a 20 amp rated 6 pole double throw switch and 25' of trailer harness wire from my local auto parts store. I ran the plow headlight wires to the where I wanted to mount my 6 pole switch. I tested the hi/lo beam switch on the floor to see which wires were for the hi beam and which was lo. There were three wires going to the hi/lo beam switch. One of them got power when the headlights were turned on. The other two flip-flopped when I hit the switch. So, the one that always had juice when the headlights were on did not need to be cut. The other two, I cut. I then ran new wires from the hi and lo to the 6 pole switch and connected them to positions 3 and 4 (middle two terminals on the switch). So now I had juice running to the switch for hi and lo. I then connected the new wires that I had run from my plow headlights for both hi beams to terminal 1. I connected both lo beams for the plow lights to terminal 2. I then ran new wires from my 6 pole switch back to the floor switch and connected terminal 5 to the old hi beam wire and terminal 6 to the old lo beam wire. So, now when you flip the switch up, it'll send the juice to the top two poles on the switch (terminals 1 and 2) and when you flip the switch down, it'll send the juice to the bottom two poles on the switch (terminals 5 and 6). One side was hi beam (terminals 1 and 5) and the other side was lo beam (terminals 2 and 6). I decided that I'd make the top poles on the switch my plow lights and the bottom poles my regular headlights. This made sense to me because the plow lights are mounted higher on the truck so flip the switch up for the higher lights. The only thing that doesn't work is the hi beam indicator on the dash when I have the plow lights on. I've got to find the wire for this and run a jumper from a plow hi beam wire to it.

Top recap, you're basically just taking the juice that is sent out of your hi/lo beam switch and sending it to a switch that will either send it to your plow lights or your regular headlights.

For the plow parking lights and turn signals, you just tap them into the factory wiring harness so they come on when you turn your regular parking lights/turn signals on. I just tested the wires that ran to turn signal/parking lights in my headlights and tapped them.

Once I got the grasp of the whole concept, it was easy to execute. The only other thing I had to do was put in a larger capacity flasher on my fuse panel. The one I had in there wouldn't make all the new turn signal lights flash on top of the OEM turn signals. I went from only flashing 4 bulbs to now flashing 8. That cost $5 from Autozone. I was also sure to solder and heat shrink all connections under the hood.

Donesky!!!!
 

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You certainly could do that but i don't think you'd want to. Then your plow lights would go on whenever your running lights were on. I would think that you would want to be able to switch between your plow lights and your regular headlights, right?

I just wired mine up the old fashioned way without relays. It took me a while and a bunch of reading to get my head around how to do it. After all my homework, I'll try to explain it as simply as I can. Bear in mind I've got a 1990 Ford F150 with a floor mounted hi/lo beam switch.
Triggering them from the marker lights makes it simple and easy.If you need your plowlights,your running lights should be on too. If you just select the running lights,the plow lights come on. This only works well if you don't have DRL's,or can easily disable them.Granted,you will have both plow and headlamps if you turn the headlights on,so this works best with a plow that has removeable headgear.If not,you can just use the plow lamps only for driving with the plow off.

If you run a ground thru the plow connector (like a fisher or western unimount style),then the lights are fully automatic. Short easy wiring (less amperage loss), brighter lights,and no switches to burn out.

One single DPST relay is all you need. Fused wire from battery to pin 30.Plow lamps tied together to pin 87 (if you find a fog lamp relay with two pin 87's it's easier,one for each plow lamp).Pin 85 is tied into the marker lamp circuit,and pin 86 goes to ground (this can be run thru a manual switch or grounded thru the plow when it's on).

So when current flows from thru pin 85 from the marker lamps to ground on pin 86,it triggers the relay connecting pin 30 and 87 and powers the headlamps.

This is for low beams only,which is all most people need for a simple cheap plow setup.

If you want the truck lamps to switch automatically,and have high beams,that can be done too,but require headlamps adapters,and a few more relays.This setup is usually easier and cleaner than a manual switch in the truck,with all the headlamp wiring run to it.
 

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wish I would have seen this one earlier, I started with nothing but the lights for the plow, taped in to the turn signals, taped into the wires from the dimmer switch in the steering wheel and ran the wires to a toggle switch so I could switch between the truck and the plow. Then I ran the wires out thru the factory loom and joined them with the turn signals, put a end on them so I would have a way to unplug the lights if I need to. Took a little to figure out which wire comeing from the steering column was what but it looked good and works perfectly, took some time but well worth it. The new,to me, one that I am putting on the good truck comes with the relays so it is automatic.
 

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The internet is actually awesome when I can have a problem solved in 2020 by reading a conversation that began in 2006! I have a 2002 GMC 2500 HD that I installed a Meyer plow on and have been wanting to get everything right with the plow lights. I usually only plow around our property but would like this truck to be legal to take elsewhere to plow. Looks like the relay with the coil power coming off the running lights and the light power coming from a fused battery connection with a switch on the dash is the way I will go.
 

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You certainly could do that but i don't think you'd want to. Then your plow lights would go on whenever your parking lights were on. I would think that you would want to be able to switch between your plow lights and your regular headlights, right? I just wired mine up the old fashioned way without relays. It took me a while and a bunch of reading to get my head around how to do it. After all my homework, I'll try to explain it as simply as I can. Bear in mind I've got a 1990 Ford F150 with a floor mounted hi/lo beam switch. Let's start with the headlights because they are the semi-confusing part... I bought a 20 amp rated 6 pole double throw switch and 25' of trailer harness wire from my local auto parts store. I ran the plow headlight wires to the where I wanted to mount my 6 pole switch. I tested the hi/lo beam switch on the floor to see which wires were for the hi beam and which was lo. There were three wires going to the hi/lo beam switch. One of them got power when the headlights were turned on. The other two flip-flopped when I hit the switch. So, the one that always had juice when the headlights were on did not need to be cut. The other two, I cut. I then ran new wires from the hi and lo to the 6 pole switch and connected them to positions 3 and 4 (middle two terminals on the switch). So now I had juice running to the switch for hi and lo. I then connected the new wires that I had run from my plow headlights for both hi beams to terminal 1. I connected both lo beams for the plow lights to terminal 2. I then ran new wires from my 6 pole switch back to the floor switch and connected terminal 5 to the old hi beam wire and terminal 6 to the old lo beam wire. So, now when you flip the switch up, it'll send the juice to the top two poles on the switch (terminals 1 and 2) and when you flip the switch down, it'll send the juice to the bottom two poles on the switch (terminals 5 and 6). One side was hi beam (terminals 1 and 5) and the other side was lo beam (terminals 2 and 6). I decided that I'd make the top poles on the switch my plow lights and the bottom poles my regular headlights. This made sense to me because the plow lights are mounted higher on the truck so flip the switch up for the higher lights. The only thing that doesn't work is the hi beam indicator on the dash when I have the plow lights on. I've got to find the wire for this and run a jumper from a plow hi beam wire to it. Top recap, you're basically just taking the juice that is sent out of your hi/lo beam switch and sending it to a switch that will either send it to your plow lights or your regular headlights. For the plow parking lights and turn signals, you just tap them into the factory wiring harness so they come on when you turn your regular parking lights/turn signals on. I just tested the wires that ran to turn signal/parking lights in my headlights and tapped them. Once I got the grasp of the whole concept, it was easy to execute. The only other thing I had to do was put in a larger capacity flasher on my fuse panel. The one I had in there wouldn't make all the new turn signal lights flash on top of the OEM turn signals. I went from only flashing 4 bulbs to now flashing 8. That cost $5 from Autozone. I was also sure to solder and heat shrink all connections under the hood. Donesky!!!!
Great article! Where you mount your relay ? Thx
 
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