Wire Size--backup lights

[Johnny5]

I will be installing a pair of 55w watt tractor lights as aux backup lights and I am wondering what wire size I should use. I will be setting them up on their own switched circuit. Also with 110 total watts, should I install a relay?



Johnny5

 

[Richterno1]

I would use 12 to 14 gage wire and always use a relay and fuse 15amp.

 

[rfcom]

Wire size

Definitely use a relay. If the relay is in the front of the truck, use one that has the dual output terminals so that you can run a seperate wire for each light, in which case AWG16 will suffice. If you run a single wire to both lights, use AWG14. You should also run seperate ground wires from each light. HTH



Jim

 

[wlowe]

Yes to relay. Also, here is a link to wire size info.



http://www.susquehanna.com/susq/other/wiring.htm



Good luck,

Bill

 

[Johnny5]

What is the advantage of running seperate power wire to each light? Just to be sure of something, the fuse on the power should be before the relay?



Thanx guys...



Johnny5

 

[rfcom]

Seperate wires

I guess I should have elaborated more. On a long run, such as when the relay is in the front and the lights are in the back, running seperate wires allows you to use smaller wires than if it was a single wire. It's a matter of voltage drop along the wire as indicated in the charts referred to by wlowe above. It also allows you to service one light without affecting the other. As for the fuse, it should be as near as possible to the power source in order to minimize the length of unprotected wire, so, before the relay. HTH



Jim

 

[Johnny5]

Thanx Jim... I figured that but I just wanted to know for sure... I constantly second guess myself especially since I want to do things correctly the first time and I have little experience modding out a truck. Hearing it from someone else makes it more believeable.



Johnny5

 

[Steve St.Laurent]

I just put a set of 55w tractor floods on my truck for backup lights. For now I just have them coming on when the regular backup lights are on. What I did was use a relay and tapped into the positive wire to the factory backup lights for the switch (attached the relay to the bed inside the light cavity) and tapped into the wire that feeds the + terminal on the trailer plug for the power feed. I plan on hooking up a switch to it as well and to do that I plan on just connecting the switch to the backup light switch at the transmission. Using this method I didn't have to run any wires to the back of the truck. I used 14 gauge wire for the feed line to the lights and grounded the lights right at the mount.

 

[rfcom]

I considered doing it exactly like Steve did, but I wanted a switch to control the operation, so there is wiring to the cab anyway. In the "off" position, the lights come on whenever I put it in reverse. In the "on" position, the lights come on, if the key is on or in acc. position. To prevent powering the trucks backup lights when the switch is "on", you need to use an isolating diode. Let's see if I can attach a drawing: