Correctly Wiring 2 Off-road Lights

YZINGERR · June 6, 2011

Im getting a pair of the pro comp 9851 lights and want to know how to properly wire them up.

I have seen some diagrams online, but am still unsure of what relay I need and how to properly connect the wires to the relay.

I assume since the lights draw 7.08 amps each, I will need a relay that will handle atleast 14.16 amps.

I see 40a relays everywhere and I assume they will suffice.

I am not sure how many pins on the relay I need (again I assume 3), but it seems like most of the relays are 4-5 pins.

Please put it into laymans terms for me, thanks!

2004 1500 silvy

Matt_ · June 6, 2011

a 30 or 40 amp relay is plenty for running 2 offroading lights.

All you need is 1 4-pin relay.

Check out this thread:

http://www.xk-forum.com/showthread.php/847...-4xGuard-Matrix!

I just wired up 4 9" lights on my Commander.

YZINGERR · June 7, 2011

Nice job!

I bought the relay and it has a diagram on it.

I am curious why the illuminated on/off switch needs 3 input wires to it (relay, ground, and pos)... doesnt the relay supply power????

Matt_ · June 7, 2011

The switch provides power (low amperage) to the relay. The relay then provides the high power to the accessory. The point is to keep the high power wires away from the passenger compartment and to decrease the length of the supply wires. The longer the wire the greater the voltage drop and more heat generation.

The switch has 3 prongs. One is the supply from the battery. One is the ground which allows it to light up. And the 3rd is the output that powers the relay.

The way the relay works is via a coil. ... when you turn the switch on power is provided to the coil which creates a magnetic field that activates the contacts of the other two terminals, thereby providing power to the lights. The ground on the relay is completing the "switch" circuit.

Matt_ · June 7, 2011

Don't forget that you need a fuse between the battery and switch AND a fuse between the battery and relay. The fuses should be as close as possible to the + terminal.

YZINGERR · June 7, 2011

Don't forget that you need a fuse between the battery and switch AND a fuse between the battery and relay. The fuses should be as close as possible to the + terminal.

I am currently trying to find a power source to the switch. a 5a fuse to the switch should suffice when I find a power source, correct?

Matt_ · June 7, 2011

Yeah 5a is plenty for the switch. A common source to use is the accessory wire coming from the ignition switch... this'll make is so the lights will only work with the key on.

I ran a power wire to my switches from the battery. The Commander has some extensive electrical systems so I wanted to leave the factory wiring alone.

Doug_Scott · June 8, 2011

Don't forget that you need a fuse between the battery and switch AND a fuse between the battery and relay. The fuses should be as close as possible to the + terminal.

You should put a fuse line out on the relay, it resides between the relay and the lights. This will protect your relay and the harness before the relay.

It is not unheard of for relays to stick on as well. Make sure you get relay designed for aux power or aux lights. You need a relay with 100% duty cycle as well.

Matt_ · June 8, 2011

I usually run a fuse that's enough for the accessory but well under the max for the relays and wiring. For example I stick with 14 gauge wire for my runs (may have very short runs of 16 for the connectors) and either a 30 or 40 amp relay... then put a 20 amp fuse in which is plenty for 2 100 watt lights. That fuse will blow long before the relay or harness gets damaged.

Not saying another fuse is a bad idea. But it adds another link/connection which has potential for issues. So since its somewhat redundant I don't bother.... but if you're sizing all of your wiring so it'll be run at max capacity then yeah, i'd probably give it a 2nd thought.

So i guess what i'm really trying to say to the OP is, FYI get 14 gauge wire even though 16 is rated for the current you're going to be drawing (12 would be overkill though)

YZINGERR · June 8, 2011

Yeah 5a is plenty for the switch. A common source to use is the accessory wire coming from the ignition switch... this'll make is so the lights will only work with the key on.

I ran a power wire to my switches from the battery. The Commander has some extensive electrical systems so I wanted to leave the factory wiring alone.

i just finished it up, i hijacked the cigarette lighter receptacle pos wire and jumped it to the switch... i hope that is ok! i figure it is already fused and it doesnt get used anyhow

Doug_Scott · June 8, 2011

Yeah 5a is plenty for the switch. A common source to use is the accessory wire coming from the ignition switch... this'll make is so the lights will only work with the key on.

I ran a power wire to my switches from the battery. The Commander has some extensive electrical systems so I wanted to leave the factory wiring alone.

i just finished it up, i hijacked the cigarette lighter receptacle pos wire and jumped it to the switch... i hope that is ok! i figure it is already fused and it doesnt get used anyhow

Is the lighter a switched circuit now? They used to be live all the time in the olden days.

YZINGERR · June 8, 2011

Is the lighter a switched circuit now? They used to be live all the time in the olden days.

it is a live wire. i wanted to be able to use the lights without the ignition being on. i camp in remote areas and it is nice to have light without the truck being "on". hopefully this setup wont drain the battery.