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Help wiring lights w/relays

4739 Views 12 Replies 6 Participants Last post by  WESBC
I just got a pair of lights that fit in fog light portion of my ARB bumper. I've been waiting to rewire my electronics correctly and have kept pushing it back till now. Currently, my Hella's and compressor are wired without a relay, and i'm still kind of unsure about it. I did a bit or searching and came up with some information.

I ended up drawing a diagram for how I plan to wire my lights/compressor and want some feedback on it. I'm still new to wiring things correctly, afterall, I did fry my GPS last week :(, so I'm not sure if what I have makes any sense at all.

Heres the diagram I made:

One question I have still is the middle prong on the switch. I used the pic below as a reference. It says to connect it to a fuse block or to the battery. So should I just connect it to the blue wire, connect it directly to the fuse block, or am I completely wrong about both.

-Thanks in advance
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Your diagram is almost right. Prongs 85 and 86 is the "trigger" side of the relay. This is where your SPST rocker switch needs 12Vdc comming into it on the center pin of the switch. the left side is OK to ground if it has a light in it. If it does not have a light in it, it would then be a SPDT switch and then you would hook the center and only one other side up. In your diagram relay 30 is correct and the voltage going out of the relay sould be on prong 87 which is correct also. Do not ground the relays prong 87a. It will short things out and cause the battery to drain if the wires dont melt first. Prongs 30 to 87a are the NC (normaly closed) side of the relay. Hooking this side up is the same if there is no relay in the circuit at all and makes no diffrence (always passes current to the load. prongs 30 to 87 is the NO (normaly open side. this is the side that gets switched when 12Vdc is sent to prongs 85 and/or 86.

So here is how I would wire things. run wire from the B+ on the battery to prong 30 with a 10awg or larger wire. Prong 87 to lights + post and other side of lights to ground. Prong 87a not used. Tap splice off the cigaret lighter wire or other ignition 12 volt source that works only when the FJ is powered on and running to your switch center pin if that is not labled ground, From the right prong on the switch, then wire to prong 86 on the relay. Ground relay prong 85 to metal. A relay needs 2 diffrent 12Volt sources to work. A relay is used to switch power to two diffrent sources or used to power a source on/off when a SPST switchs current rating is less than the amp rating of the load. All your are really missing is the 12v 2nd source to go into the center prong on the rocker switch. Good luck.
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Thanks Ace! I hope to have these wired up to OEM switches after the M&G
the switches need power to work.

Like this.

You can also put a fuse inline to the fuses it you like.
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jeshua said:
the switches need power to work.

Like this.

You can also put a fuse inline to the fuses it you like.
This is correct. And is one of 2 ways to do it. The only draw back of doing it this way is if your truck is off key out and you forget to switch off the rocker switches your lights will remain on. Just remember to power everything off and you should be fine. Thanks Josh for drawing this out.
No problem. I have been drawing my own wiring diagram up the last 2 weeks trying to get everything planned out for when I do the wiring in a week or so. Now I am waiting for my shipments of wire, switches and bus bar.
one of these days i'll get off my ass and hook up the lights on my roof. that would require drilling a hole. since there's no turning back after that, might as well get a snorkel too. my logic is undeniable.
GTKrockeTT said:
one of these days i'll get off my a$$ and hook up the lights on my roof. that would require drilling a hole. since there's no turning back after that, might as well get a snorkel too. my logic is undeniable.
I'm in the same boat. I did get them mounted to the bar, and wiring run through that to the rack. Now, I need a new RIVNUT, and the courage to drill a hole in my roof.
What gauge wire should I use?

Aux lights- 55w/12v = 4.58 Amps
Compressor- 30 Amps

Using the chart below

Lights- 20 AWG
Compressor- 8 AWG

The gauge recommended for the lights seems to low, is this okay? Or should I just use 18 or maybe even 16 gauge wire?
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I would run 8awg from my battery to my fuse block/holder. Run 10awg to my lights and also to my compressor. I would use 18 or 16awg to my switches. They will not pull any current per-say. Use the same gage for grounding also. Use 30 or 40 amp relays I would also use a inline fuse at the battery + post and as close to it as you can. Like the one used for a car stereo amp. 50 amp fuse would be fine. 8awg is rated to 50 amps. So is 10awg at 20 feet, which should be enough length to get to the rear of your rig. Good luck. That figure of [email protected] = 4.5 amps seems really high if that is per light for current draw. in a house a 100w light bulb only draws about 1Ahr. But who knows, I'm not a 12v guru.
I used 16 gauge stranded for my lights because it was less than 10'. For longer runs I would use heaver gauge to make up for load and amp loss. As a reference, the stock PIAA wires for my lights are 18 gauge. You can't go wrong when using a heaver gauge wire, its just harder to work with in tight situations.
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