Electrical gurus, attention on deck. Tractor lights and relay question

[Desert Rat]

Ok, searched under tractor lights, rear lights, lights, etc. and read a bazillion posts but still have questions. I am planning on mounting a couple of those rubber housing tractor lights in the back for lighting up the rear. When I owned my 90 Bronco, I put a couple just under the rear bumper. I seem to recall that I simply wired them to a switch and to a power source. However, I am now thinking, after installing a set of Daylighters up front, that perhaps a relay would be in order.

Can somebody explain to me the purpose of a relay, if I need one for two of those 55w rubber housing tractor lights, and if I do, how is it wired? If I recall correctly, there was only one wire that came out of the tractor lights as opposed to the two that come out of a set of driving lights. I have a switch ready to go that I got from Wal-Mart that matches the LED lighted switch that came with my KC's. How would I run the wiring with the tractor lights as opposed to how I ran my Daylighters?

Lastly, I was in a quandry as to where to mount them. On my Bronco, I put them just under the bumper. However, on one particularly gnarly crevace I crossed, I scraped the rear bumper good and pretty much ripped off the tractor lights in the process. So, I don't plan on putting them under the bumper. In one thread I saw the Vortec mounted his on the rear upper bar of his cage at the top of the rear window. I am inclined to go this route since my main purpose for them is to give me light when backing up, and also for extra lighting in camp when cooking on the tailgate or unloading. I am open to other suggestions though.

 

[Desert Rat]

Come on, I know some of you are the shiznit when it comes to electrical. Me, I'm lucky I don't electrocute myself frequently.

 

[lectric80]

Based on your stated goals, a relay wouldn't be a bad idea. The main purpose of a relay in this situation is to reduce the amperage going through the switch, while still providing plenty of amps to the lights.

In this situation you would have power running to the relay, then from the relay to the lights. The switch would have a 5 amp or less power source run through it to the relay switch point (I forget the numbers on the relays) that would activate the relay. You would also need a ground for the relay and that is the wiring.

As for mounting I can't be of much help, but since you want it for backing up and for lighting the tailgate area when cooking, the roll cage upper bar should work fine. Just remember, if the window is closed, you are going to get an ungodly amount of glare inside the truck.

 

[Desert Rat]

Thanks for the reply. Once I purchase the lights, do I then go and match the relay amperage with the lights? Having never purchased a relay outside of having them included in a kit, I am assuming that they make different ones.

 

[Ryan B.]

Watts = Volts x Amps.
55 Watts / 12 Volts = ( ? Amps) ... = ~ 5 amps each light.
So you'll be drawing ~ 10 amps for the two lights.
Most Bosch or Hella relays will say on them 30 Amp, so you should be good.

A Relay has 4 or 5 prongs, You only need a relay that has 4 prongs, and is normally open.
Pins 85 & 86 are the field coil, what makes the relay click and turn on.
When 85&86 have power and ground the relay will switch, and pin 30 will click over connecting to pin 87.

85=12v turn on signal (stock reverse lights, or 12v switch)
86=Ground
30=Thick 12v power from a 10+amp fused battery source. (run it from the battery, do not tap into the fusebox somewhere.)
87=To your new lights.

 

[Desert Rat]

Not having one in hand, that sounds confusing but I'm sure if I go and pick one up I will be able to use that as a guide. Thanks much. I pre-installed the switch and ran extra wires through the firewall when I did my front lights so I think the relay and light purchase will be done today.

 

[Desert Rat]

Just remember, if the window is closed, you are going to get an ungodly amount of glare inside the truck.

I'll definitely have to have the window rolled down at least a bit when I use them. Maybe I should throw a third light in the center of my tire carrier.

 

[dremu]

Ok, searched under tractor lights, rear lights, lights, etc. and read a bazillion posts but still have questions. I am planning on mounting a couple of those rubber housing tractor lights in the back for lighting up the rear. When I owned my 90 Bronco, I put a couple just under the rear bumper. I seem to recall that I simply wired them to a switch and to a power source. However, I am now thinking, after installing a set of Daylighters up front, that perhaps a relay would be in order.

Can somebody explain to me the purpose of a relay, if I need one for two of those 55w rubber housing tractor lights, and if I do, how is it wired? If I recall correctly, there was only one wire that came out of the tractor lights as opposed to the two that come out of a set of driving lights. I have a switch ready to go that I got from Wal-Mart that matches the LED lighted switch that came with my KC's. How would I run the wiring with the tractor lights as opposed to how I ran my Daylighters?

Lastly, I was in a quandry as to where to mount them. On my Bronco, I put them just under the bumper. However, on one particularly gnarly crevace I crossed, I scraped the rear bumper good and pretty much ripped off the tractor lights in the process. So, I don't plan on putting them under the bumper. In one thread I saw the Vortec mounted his on the rear upper bar of his cage at the top of the rear window. I am inclined to go this route since my main purpose for them is to give me light when backing up, and also for extra lighting in camp when cooking on the tailgate or unloading. I am open to other suggestions though.

You *know* you could just ask ... sheesh.

A 55W light will take about 5 amps. Your average black square Bosch-type relay is good for 20 to 30A, so you can do four to six lights per relay.

A relay is basically a switch, but higher capacity than your regular toggle switch.

So the toggle switch sends a very small amount of juice (<1A) to the relay, which then switches the higher current to the light.

It's like the starter solenoid, right, you don't have 200A flowing through your ignition switch; the switch turns on the solenoid which lets the crazy amperage flow to the starter.

If you like, pick an afternoon and buy me a burrito and I'll swing out and wire it all up for ya, easy.

-- A

 

[Desert Rat]

PM'ed you back. I'm going to try and do this today but if you see a bright light in the sky, pay no attention, just pretend it is the lab going up.....

 

[Desert Rat]

Ok, wrapped up the project today. Thanks to DrEmu, lectric80, and RyanB for the help. I used your posts along with the schematic that came with my Daylighters and was able to figure it out. The project came off better than I expected. I fabbed up some L tabs and combined them with U-bolts to fasten the lights to the rear of my roll bar cage crossmember. Then I ran the wires up to the relay. I copied the setup for the Daylighters and put in some in line fuses between the battery and the relay and the switch and the battery. I used the same LED switch that KC uses so it matches in style but with a different color LED. I swapped out the nut on the bolt that holds the light in the bracket for a wing nut. This allows me to adjust the angle so that I can light up the rear area, or angle them down and light up the rear tailgate for cooking etc. when camping. I am maxed out on my picture albums so if anyone can tell me how to embed pics from a Webshots account, I can put them there and link them, provided Webshots allows linking.