Trailer Wiring Questions

[TKingsbury]

My truck has the trailer wiring tapped into the wires at the rear. No problems yet, and I tow maybe once or twice a month. One of these days I'll probably do some relays though. Might start looking for a nice fuse/relay box from something in the junkyard to use.

Travis. .

 

[JZellers]

After reading this I figured that I should fix mine sooner than later, since my wiring is all tapped in at the rear and I'm not really in the mood for a cab fire I picked up 3 30A relays last night for $3 a piece. I live in the midwest so moisture/salt is a concern as the relays aren't exactly weather-proof. From my recent generator transfer switch wiring project I got the idea to try one of those PVC all-purpose electrical junction boxes that you can get in different sizes at Menards/Lowes/etc. for a reasonable price. An o-ring or gasket around the cover and some grommets to seal the wires entering/exiting should work and also allow a neat mounting of the relays inside the box.



I personally like the isolater idea because it's a clean install but I also had feedback problems in the past. I all my cases it was the 1157 bulbs in the tail lights that did it. If the brake/turn fillament either broke just right or otherwise collapsed on to the other, all the lights would come on when I either pressed the brakes or used the turn signals.

 

[JLEONARD]

Jay if yours is a standard D model without all the extra lights

Phillip,

Ok Thanks. I won't worry

 

[Greenleaf]

Jay,



If I wrote you and told you your truck will burn up, would you beleive me?



Set back with a Mt Dew... ... er beer in your case, and take it easy. Watch everyone else rewire their trucks.

 

[R C Cola]

Trailer wiring & relay Answers !

Finally got it ! Thanks for all the input. For those who are still working on it here is what I ended up with. Needed more clarity so the first thing I did is subscribe to All Data for my truck. $25 Bargain Wanted to keep relays etc in front to protect from road crap. Located signal wires going to Stop, and Turn, in dash loom coming from steering column used a 3 way crimp on tap (NAPA) on each outgoing wire, Dark Green/Yell for Left and Brown/Yellow for Right.

These 2 wires (left and right) are marked and then run thru firewall for signal to the relays. At the relay this supplies minimum 12 v needed to fire the relay contacts. Each relay must be grounded to function so I looped the(Did that with incoming 12v supply also) wire to minimize clutter. Used 12 AWG from battery source for power (fused 20A) to go thru relays to trailer connector. Again (2 needed)12 AWG out of relay to rear of truck to the trailer connector. Signal to fire the relays is minimal and small wire could be used. I used 12 for that also since had it on hand. Suggest wire markers and a notebook for later referance of which is which, as correct colors are hard to come by when buying wire.

Brake, turn, and Emergency Flashers now have their own supply to the trailer connector. This site is a huge help to me and hope this helps others save themselves some road trouble and/or fire in truck. R C

 

[MViau]

Trailer wiring installation

I thought this was a great thread and after reading the post i thought I'd share a picture of the installation i did on a seven pin. View attachment 64969

 

[Niki]

I'm pretty sure Chevy has been completely isolating the trailer wiring from the taillights for quite a while, I'm sure Dodge and Ford do also. Separately fusing/relaying trailer wiring is a good idea not just to handle the extra load, but to isolate. Trailers are often neglected especially in the wiring department. Wiring may be the first gen trucks biggest weakness. A fusebox that you have to unscrew part of the dash to get to then it hangs by wires, fusible links... Plus over the years there has been CB's, trailer brake controllers, car phones, stereos, etc installed, all adding to the mess. Whenever wiring in a car/truck, take the extra time to do a neat install, and fuse/relay as required. If nothing else, it'll make the next owners life easier.

 

[WJones]

I've been contemplating doing something like this for a while, wiring it up is easy however id like to find some sort of weatherproof box to put the relays in under the bed. havent seen anything yet though.

 

[DVolk]

Sevral years back i had this issue on a trip to K falls,Ore



I was blowing fuses right and left , i changed the fuse same thing happend



I went and chaged both the 4 way and normal turnsignal flasher with the

extra heavy duty loud ones a truck stop the problem went away and never reacured again but it was a $30. 00 fix though

 

[Moab4x4]

I see heat as the killer. My HL switch was starting to discolor from the heat of the electrical current through it. The thought I had was that not all lights are used continuously, Headlights and taillights only.

I used two relays under the hood, one for High beams and the other for Low with both powered by the same 30A breaker. IIRC I wired them so both would be on when I wanted brights. (the way a brite box does) It's been long enough now, I don't remember the details well.

I used one relay under the dash for the tail/parking lights with it's own fused power. I know this uses the factory tail harness, but I don't tow trailers that are lit up with a bazillion marker lights either. I might run a larger gauge wire for the trailer marker lights if I was, but I would not put the relays under the truck without good waterproofing. Running an extra wire is easier.



If you are going to add many circuits to your truck I recommend fusible link wire by the battery. You can buy a 10' spool of fusible link wire at NAPA for the price of two 6" precut links.



But then again I am an electrical nerd and ran #6 to a point behind the glovebox and now have two fused power take off points there, one on BATT, the other on IGN.



Ignition- isn't that a bit of a misnomer on our trucks?:-laf

Ken

 

[WJones]

Im not a fan of fusable links, Ive replaced most of mine with self-resetting breakers.



for isolating my trailers lights I ran a piece of 12ga down the chasis to a plastic hobby box i bolted to the frame rail next to the trailer plug. A little bit of silicone and it should be water tight.