Wiring roof lights

[ChopTop84]

here. try this on for size. If your lights are 100w bulbs, then use it as it. If they are 50w bulbs, then you can lose one relay, and gang all 4 lights off one relay.


.... try this again....

 

[1Jesusfreak]

Thanks. Am I using all five pins on the relay or just four and do I have to go to the headlight switch if am going to use a separate on off switch? Like I said I am a little slow when it comes to all of this and lots of detail.

 

[ain'tstuckjustresting]

Nope, just 4 wires. Use the normally open pin for power to the lights and leave the normally closed pin unhooked. You can grab power for the switches from any fused source.

 

[ChopTop84]

Yup, what he said. I just listed that 5th pin because its there and at least now you know what its for. (The extra pin acts as a flip-flop. when 87a is hot, 87 is cold, then, when the relay turns on, 87a goes cold, and 87 goes hot. It has its uses, just not here).

The reason I put the wire to the light switch is, its usually pretty close to where you are prolly going to put your switch, and you have several options of what wire to grab power from, and they are usually fused already, so you shouldnt need an extra fuse to the switch.

 

[1Jesusfreak]

Thanks. Just went out and checked the lights and they are 100w. So it looks like I will be running two relays with two lights each.
Not sure if this can be done, but I did find a 70 amp relay. Can that be used in the place of the two 30 amp relays or am I asking for probs. Just wanted to ask.

 

[ChopTop84]

Thanks. Just went out and checked the lights and they are 100w. So it looks like I will be running two relays with two lights each.
Not sure if this can be done, but I did find a 70 amp relay. Can that be used in the place of the two 30 amp relays or am I asking for probs. Just wanted to ask.

Hmmm, 70 amp? I prolly wouldnt use cheap crimp on connectors, at least not the ones you get at the parts store. (I had an awesome crimper at my last job that could do up to 4-aught wire, thats as big as your thumb!). You can absolutely use anything thats rated for the power flow you intend to use. 4 lights of 100w each is gonna be in the 40amp range, so 70 is well within spec, just make sure you use a large enough wire and fuse. Your going to be looking at either MAXI-fuses, or the larger bolt in fuse like the ANL style. You can get the larger amperage stuff from West Marine, because most boats deal with some pretty large amp ratings, whereas automotive stores seem to limit themselves to about 30 amps max.

With the diagram I posted, you should be able to do everything with automotive grade parts store stuff. To do it with one wire, and one relay, your going to need something larger than most local parts stores carry, unless they deal with high amp stuff on the side.

As for amperage ability of a given wire size, thats a tricky area. All depends on whose rules your trying to meet. Coast Guard/ABYC rules have 10% and 3% voltage drop rules depending on the circuit. That results in some pretty large wire for what should be simple circuits. Automotive grade wiring rules are horrible. My Superduty uses 18ga wiring for the headlights! There is like a 2 volt loss of power from the battery to the lights because of that. My headlights were only getting like 10 volts! Thats why they sell "upgrade harnesses" for headlights on cars and trucks. I would do nothing less than 10ga to your lights. If you do it all from one relay, I would be tempted to go to even 8ga wire, at least to the first light, and daisy chain 10 gauge to the rest, but run an 8ga ground back to the frame/body.

Its up to you tho. Most parts stores only sell up to about 12ga wire, so thats what most ppl use, and that is actually fine, but they are not getting 100% power to their lights.

 

[1Jesusfreak]

Thanks ChopTop84. I think I will go with the two relay setup and that is because of cost. The 70amp relay that I found on line is not cheap and I don't think the fuses for that kind of setup will be either. Found a five relay on ebay that I may get so that I can other things in the future.
You have been of great help.:awesomework:

 

[ain'tstuckjustresting]

30a relays are only like $6 at Napa. The added cost of running bigger wire would more than offset the cost of the relay. The 2 relay is the better option for sure. If it were me I would run 2 seperate switches. Just because 400w is alot of light and you might like to be able to select 2 or 4 lights. Could also turn 2 lights backwards later and be able to shut them off if someone was behind you. Just my $.02:awesomework:

 

[1Jesusfreak]

ain'tstuck, I like the idea of using two for the rear of the rig, had not thought of that will have to think about that