2nd Gen Non-Engine/Transmission Trailer brake wire from cab to 7 way

[schlepn]

I have a 4 way trailer plug on my truck, have mounted my 7 way( 4 way plugs in to 7 way for tail, stop & running lights ) and plugged in my brake controller to the factory plug under the dash, where do I find the blue wire to hook to the 7 way blue to power the trailer brakes, my truck did not have towing package from the factory, I am assuming I have to run an new separate wire from the wire harness under the hood to the 7 way, I have read my self silly trying to find it in any posts



Thanks in advance



Dave

 

[DGamelin]

If it didn't have a factory trailer package the wire wont be there from the cab plug all the way back. I would just run a wire all the way back from the brake controller. If you are going the pull a rv or a dump trailer. You will need a 12V wire ran also to keep your batter up. I would use a red 10 gage wire for the 12V and blue 10 or 12 for the brakes. On some with out a factory trailer package the factory plug under is not hot. you have to wire the hole thing.

Have Fun.



93 250 2wd xc 354 auto 263k

04. 5 3500 4wd cc dully 373 6speed 85k

 

[schlepn]

Thanks for the reply



The blue wire is connected to the under dash brake controller factory plug (truck side), but that blue wire that is in the factory plug on the truck side has to go some where that can be taped into is what I am thinking, I can see about 6" of it then I lose where it heads to

 

[DGamelin]

If the wire is there I would think it would be back near the rear bumper in the tail light harness and if it is then it had a factory trailer package already. check along the left frame rail and see if it been taped up some where near the rear is were it should be, or at the cab. If it is back there it should have the 12V and back up light wire to. Most of them have a tow package. Good luck

 

[DGamelin]

If the blue wire is there dont tap into it find the end of it. If it is the wright wire it is only used for brakes.

 

[schlepn]

Well this smart guy ordered his CTD and didn't order the tow package, ( did my own but just a 4 way to this point) I had repaired to many wiring problems that were factory & dealer installed, so I wanted to do my own, I read years ago that the wires were in the loom but have never been able to find them, but have the need to get the 7 way wire and brake controller hooked up, I pulled the spare tire down opened the loom up at the rear shook mount, no wires. I am heading out to see if I can find them under the cab buy the LF tire and yes, this posting is to find that little end of that missing blue wire;0)

Thanks again

 

[JonGerard]

The End of the Blue wire should be under the Dash. It should be on the Left side of the Steering Wheel Column. There is a hole in the Fire Wall where a Wire Lume comes throw. that Blue wire should be tucked in with those wires. Some times it is just on the engine side of the Fire wall. It should have a white tag on the end of the Wire Marked Trailer Brakes. Good Luck

 

[charlessmith]

If you are wiring your own stuff - here's a caution warning!



The factory tow package does not run the trailer tail light circuit directly off the headlight switch wire to the truck tail lights. The headlight switch contacts are too weak to handle much extra load. The factory setup runs a relay off the tail light circuit, and then runs the RELAYed tail circuit through the 7 connector plug.



Look under the lid of your power distribution box, you can probably figure where the trailer tail relay goes, so that will be a starting place.



I also use a relay for the +12 supply to the trailer / RV, that is switched by the ignition.

 

[schlepn]

Jon thanks for the reply, I found the end of the blue wire at the truck side of the harness down by the LF tire where there is a male/female connector, it is coming from the factory pre-wired blue 4 spade brake controller plug that is in the cab, but that wire is not present on the side of the plug that is running down the chassis to the tail lights to activate the trailer brakes, so I taped into that and ran to the 7 way and "PRESTO"

 

[schlepn]

Hey Charlie, when I said I wanted to do it myself I did not mean from scratch,(I would use a kit, which I did) with all the salt they use in MN and all the city driving I do, it kills any connection that it can get into,( and Dodge doors) the only why to prevent it is to use dialectic grease in every connection and void, when I used the aftermarket connector to tap the tail lights I did not use it trying to save time, I got 1. 5 years out of one of my connections on the tail light, it was so bad that I had to remove the plug completely, solder the wires and use heavy duty adhesive lined heat shrink tubing on the solder joints. My truck has a 40 amp fuse for trailer in the power dis box, so tail, head, brake & running lights should be protected

I taped in to the factory connectors with the aftermarket trailer wiring kit to get the 4 way plug that has been on my truck for years, I needed to step up to the 7 way plug and brake controller. I had read a post the same as your way for igniton hot/relay only(It might have been your post even) and had planed on that for 12 v power, and was also going to run a new wire for back up on trailer the same way with a heaver gauge for extra backup lights that I have on my trailer so not to tax the truck back up system, I tried to post a picture of a grease pump and needle I use all the time when working on any electrical, it works sweet. If you think I have missed any thing please let me know



Thanks



Dave



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[charlessmith]

Dave, your use of waterproof grease sounds real good. I'm a fan of that adhesive lined heat shrink tubing, the stuff I use shrinks to 1/3 the original size and still stays pliable.



The big caution is where to tap in for the trailer tail light power source. I have a web page put together that covers details on this including color of wires to tap onto: Dodge Ram - 5th Wheel & Camper Tail Light Wiring



Check the circuits through the 40A fuse, I don't think it covers the stop and turn circuits. I think it is only the +12 feed to the 7 way plug. The tail light power to the 7 way plug comes from the "Trailer Relay" in the front fuse/relay box. I rewired the internals of my fuse/relay box to use an external heavy relay activated by the ignition switch for the +12 to the 7 way plug.



After you get things connected, you can pull the 40A fuse to see what it protects ... see what pulling it shuts off.