Trailer Light Plug

[350chevy85]

Recently purchased my truck and it already has a trailer hitch on it but its seems like no one ever wired up the trailer light plug and i've never done any real wiring before and was wonder if i could get some advice for wiring a 7 pin trailer plug. For some reason the truck already has a break control which looks ancient and has what looks like a brake line hooked up which i assume it to determine the applied brake pressure

 

[77 K20]

http://www.etrailer.com/faq-wiring.aspx

I used the diagrams and parts from etrailer to wire up my '77. The brake controller you have is one of the old ones- as the newer ones are all electronic.

 

[89Suburban]

I only tow my boat trailer almost year round so I installed 4 way weather pack connectors for the light connections and have dummy ends to plug the leads into when not towing. This should end my battle with plug corrosion. And if I need to tow a different trailer I have an adapter wired up to fit the universal 4 way plug.

 

[chengny]

Splicing in an aftermarket trailer harness plug is not rocket science. However, it is difficult to provide a procedure to someone who has no experience with automotive wiring repairs (especially making modifications to the truck's stock wiring).

Before anyone can really help you, it may be best to:

1. Attempt to develop a procedure for the modification yourself first

2. Open the harness sheathing in an area where you think the splices might best be made

3. Clean/identify the wires you think need to be spliced

3. Get images of the particular trailer wiring kit you intend to use

4. Look into the various splicing methods (i.e soldering & heat shrinking, "vampire taps", solderless connectors) and decide which one is best for you.

Good advice here -
http://www.backinblackgp.com/Tap_And_Splice.htm

5. Gather the various tools and materials that are required to do the job

 

[350chevy85]

Thank you all with the advice I should be post in the next couple of days to see what i come up with time permitting

 

[77 K20]

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I HATE splicing/cutting/messing with a factory harness. I ordered this for my '77. Unplug factory connector, then plug this in the middle. I made sure all pins were clean and corrosion free. When plugged back together I even used a bit of silicone or liquid electrical tape to run a slight bead around the mating surfaces to seal it even better. For the ground wire I made it as short as possible to the frame, drilled the hole, then ground down around it for a better connection. After the ring lug was bolted in, I then sealed the crap out of it with sealant to make sure corrosion doesn't kill the connection.

(I also don't like any of the butt splice connectors or things like that. Can't think of how many times I've had to fix someone's trailer wiring because of some sloppy connector had corroded and then corroded the wiring. If I do have to splice a wire, I solder it together then use heat shrink and sealant on it. Never had an issue.)

So then I had a 4 way connector. It took forever but then I found other needed adapters for what I needed.

Basically I have the 4 way behind the rear bumper, that plugs into a harness I made that goes into a 6 way in the rear bumper and a 7 way up in the bed for a 5th wheel.

It is very hard to find a 4 way to 7 way adapter because you would still need to run 3 wires manually. I ran a charge wire and the brake wire all the way back in wire loom. The charge wire needs to have fuses or self resettable circuit breakers.

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