Factory or aftermarket trailer wiring

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Factory or aftermarket trailer wiring

Postby shackwrrr » Mon Mar 02, 2015 8:57 pm

How are trailer light/brake receptacles usually wired in on first gen trucks? Does OEM trailer wiring exist for more than a 4 pin connector?

Also has anyone ever added a relay center to isolate the truck and trailer wiring. My jeep had 3 relays that dealt with left, right, and tail lamps. These relays were fed by a 30 amp fuse underhood and each had their own circuit breaker. The 30a fuse also fed the B+ connection at the 7 way. I always thought this was the best way to run trailer lights, didn't know if anyone had a similar setup in their truck.
1991 w250 RCLB
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Re: Factory or aftermarket trailer wiring

Postby matthewh » Mon Mar 02, 2015 10:21 pm

As far as OEM harness, there isn't one. Typically you have to tap into the brake switch under the dash and run a wire from the control box out back.

I'd be interested in seeing a relay setup. There's a few members that have done similar setups, but I think a good write up with pics and part numbers would be awesome, for those of us who are electrically challenged. Think something similar to the headlight relay sticky on dtr would be great
'93 W350 5spd Getrag, 4.10 gears, 83k miles and counting, Mods: LPPP AKA Ma Dually
'54 Dodge M37 6.2/700R4/205, 5.89 gears, WC rear axle
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Re: Factory or aftermarket trailer wiring

Postby PToombs » Tue Mar 03, 2015 6:32 pm

I have one of those T-tap kits for the trailer plug. I cut off the 4 pin and put on a 7 way RV plug and ran the extra wires for the brakes and hot to it from the front. I put my trailer and tail lights on a relay, and didn't worry about the signals. I'm switching over to LEDS for the tail/ turn/ stop lights. My hot wire is on a circuit breaker. I put the relays under the hood. I got a fuse box from a 2nd gen gasser and used that for relays for my headlights, auxiliary fuel pump, trailer lights, and a couple other things. It was a PITA and next time I'll do it differently.
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Re: Factory or aftermarket trailer wiring

Postby thrashingcows » Tue Mar 03, 2015 9:32 pm

This is the set-up I ran on my crewcab....

I used the Reese 74182 adapter to tie into the factory taillight harness....this gave me a 4 pin light connector plug.

Image

Then I bought a Tow Right 20125 - 7 pin trailer plug. This has a 4 pin plug in adapter for the lights, then you just need to run the white wire to ground, and then run the blue wire to the under dash brake controller, and the black wire to a 30amp circuit breaker off the battery. I think that is how the wiring went. The yellow is for reverse lights on the trailer...I didn't use that one.

Image

I did it this way so I did not have to cut into any of my original wiring. Works great!
1984/93 Dodge Crewcab, W350, 1 Ton SRW, long box, 330K Km's, M&H spacer, 366 spring, fuel pin to deep side, 14cm housing, Piston LP, PS IC, Isspro Boost, Pyro and tach, NV4500, 29 spline NP205, 3.54's.


Check out the build....http://www.dieseltruckresource.com/dev/ ... 05923.html
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Re: Factory or aftermarket trailer wiring

Postby Philip » Tue Mar 03, 2015 9:35 pm

Check with a RV dealer and see if the after market trailer wiring kits are still being made. They plug into the truck harness back at the tail light connection plug.

Here is a link to one. That kit is for a 4 pin flat plug. If your going to a 7 way. Just trash the 4 pin plug. Then run a wire for trailer brakes and trailer ground.


http://www.etrailer.com/t1-1993_Dodge_Ram+Pickup.htm


You beat me to it TC :lol: :lol:
93 W350 Club/cab w/duals, buckets & console, B&W flatbed, G56, 6 spd, 3:07 rears, gages, HX40/16, 4" exhaust, 6X.018 sticks, rear air ride suspension
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Re: Factory or aftermarket trailer wiring

Postby thrashingcows » Tue Mar 03, 2015 9:36 pm

Philip wrote:

You beat me to it TC :lol: :lol:



Yes I did....by 3 whole minutes too.... ;) :mrgreen:
1984/93 Dodge Crewcab, W350, 1 Ton SRW, long box, 330K Km's, M&H spacer, 366 spring, fuel pin to deep side, 14cm housing, Piston LP, PS IC, Isspro Boost, Pyro and tach, NV4500, 29 spline NP205, 3.54's.


Check out the build....http://www.dieseltruckresource.com/dev/ ... 05923.html
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Re: Factory or aftermarket trailer wiring

Postby shackwrrr » Wed Mar 04, 2015 10:53 am

With the "T" harness setups, any issues with flashers or switches? I'd like to keep as much load off the factory switches as possible. I have a 1989 caravan with the same style switches and after 26 years they are starting to wear out.

I will most likely end up peeking around the junkyard for a simple relay/fuse box for an isolation center. Ill try to document the process the best I can.
1991 w250 RCLB
3 speed auto Non IC truck
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Re: Factory or aftermarket trailer wiring

Postby thrashingcows » Wed Mar 04, 2015 1:02 pm

shackwrrr wrote:With the "T" harness setups, any issues with flashers or switches? I'd like to keep as much load off the factory switches as possible. I have a 1989 caravan with the same style switches and after 26 years they are starting to wear out.

I will most likely end up peeking around the junkyard for a simple relay/fuse box for an isolation center. Ill try to document the process the best I can.


25+ years and the switches are wearing out...think that's a pretty darn good run in my books! ;)
1984/93 Dodge Crewcab, W350, 1 Ton SRW, long box, 330K Km's, M&H spacer, 366 spring, fuel pin to deep side, 14cm housing, Piston LP, PS IC, Isspro Boost, Pyro and tach, NV4500, 29 spline NP205, 3.54's.


Check out the build....http://www.dieseltruckresource.com/dev/ ... 05923.html
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Re: Factory or aftermarket trailer wiring

Postby Philip » Wed Mar 04, 2015 2:29 pm

Your biggest load is the marker lights on these trucks a lot of markers has been known to burn out head light switches and the plug for the switch.

Most of use put the marker circuits on a relay for that reason.

Fill out your signature so we know what your truck is without asking on every post.
93 W350 Club/cab w/duals, buckets & console, B&W flatbed, G56, 6 spd, 3:07 rears, gages, HX40/16, 4" exhaust, 6X.018 sticks, rear air ride suspension
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Re: Factory or aftermarket trailer wiring

Postby shackwrrr » Wed Mar 04, 2015 3:48 pm

Truckless at the moment. I've worked on many D/W trucks but never owned one. Looking at an 89 and a 91 this weekend.
1991 w250 RCLB
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