trailer wiring questions

[Jim P]

I have bought a 30' Jayco fifth wheeler and I now have to wire my truck for it.

My truck already has a plug for a trailer but I don't think it is wired for the battery charge wire or the electric brakes. I need some tips on where to get power for my brake controler and for the battery charge wire. Is it possible that these wires are already in the harness but just need attached on both ends?

I also have read that the headlight switch does not hold up well when pulling a trailer with alot of lights so alot of guys install a relay in this circuit. Is the relay mounted back by the plug and powered by the battery charge wire or is it mounted up under the hood?

[Phil Holmen]

Jim, what I did after finding out the hard way is added a relay to turn on the power only when the ignition is turned on. The Power other than that is supplied from one of the large aux fuses in the fuse panel under the hood. I also ran a dedicated wire at the same time for the relayed park lights. This helps keep all connections out of harms way. When I had purchased my truck the previous owner had butchered the factory installed towing wires to add provvisions for a 7 blade and 5 pin connector on the hitch as well as a 5 pin in the box for a stock trailer. I went to a local highway tractor supplier and got a weather proof box and ran a separate 7 wire cable from all of my plugs to the box, replaced the 5 pin in the box with a 7 blade rv plug and now I have a weather tight connection area if I need to change anything.

[HowieE]

On the 95 you will find the ends of a large blue and a large orange wire tucked under the steering colume against the firewall. They may be wrapped back into the harness but you should be able to see the colors sticking out as the loop back into the harness. You will find the other end of these wires tucked back into the frame rail on the drivers side just forward of the rear bumper. Gm supplied them for trailer battery and trailer brakes. I use the larger diamater wire for my brakes to reduce voltage drop over the distance.
There are 2 vertical posts on the back of the under hood fuse panel that you can pick up fused power from. There is a horizontal stud on the drivers side of that fuse panel the is battery. Use that stud to supply you trailer brake through a 30 amp circuit, if you have 4 brakes on the trailer, you install on the firewall

Yes on a trailer as large as yours it is a good idea to relay your parking lights on the trailer to reduce the chance of melting the parking light circuit in the head light switch. Check my site for the results if you do not relay, http://mysite.verizon.net/vze54tx9/.
I installed the relay in the trailer and use the trailer batteries, I have 2 batteries in the trailer, as a source for the trailer parking lights. Others install the relay in the truck and use the truck batteries as a source. The advantage to this method is if you intend to tow different trailers and do not want to wire each trailer.

Considering the wire sizes GM used I also relayed my brake lights with the relays installed in the trailer and again useing the trailer batteries as a source.

Bully Dog is a good source for the relays and sockets.