Towing Harness -- Factory Harness to Aftermarket 7 Pin

[ShadowFox]

Found out that the 7 pin on my truck was shot from weather getting to it. I went to Autozone and bought one of these:

Multi-Tow® 7:4 Ford//Chevy/GMC

As you can see, the end of that Hopkins plug is round. The harness that is on the truck is square...like this:



I learned at an early age that I can fit a square peg into a round hole. So I was just going to splice the wires from the Hopkins into the square connector and reuse that. Well all the colors for the wires on the Hopkins match up to diagrams that I find on google, however they do not match the colors on the factory harness. Can anyone tell me what colors from the factory harness go to the 7 pin?

Thank you!

[Big Jeremy]

This is the best i can do for you. http://www.etrailer.com/faq-wiring.aspx
If the trailer is wired correctly, just use a test light on the trucks wiring to match up to the trailer / color chart.


Big Jeremy

[jerg_064]

Depends on the year of the truck....Best way to tell is get a multimeter or test light and check where the signals are...

What year is your truck? If it's a 99-01 they still sell a harness for it that has the factory square connector you showed to hook up to the truck. If it's later than hardwiring is the best was UNLESS you want a T-connector with a 5th wheel connector as well.....Check out jesilvas's thread that's in this forum.

[ShadowFox]

Thank you for the responses and I apologize for not being proactive with this thread. I was a little preoccupied with my funeral...err...wedding. However now things have settled down.

My truck is a 2001. I did find that square harness and picked one up as my father in law needed to use my truck to haul a trailer. Well I plugged that in and it gave the same result as the auto zone harness that I spliced in. So apparently I spliced the auto zone piece correctly, however my issue must be somewhere else. I did find out, however, that if the brakes are applied to the truck when attempting to use the trailer lights, they seem to work properly. The only issue I can think of is a bad ground somewhere. I plugged two seperate trailers (7 pin and 4 pin) to my truck and received identical results. I also plugged the 7 pin into a newer GM truck () and all the lights worked perfectly. I'm guessing that I am going to have to try and trace all the wires back to their origins and possibly redo the trucks wiring for the trailer.

Can anyone tell me where all of the wires for the trailer harness begin?

[jesilvas]

Hey, that pic looks familiar.
Trailer tow TRUCK harness connector
So what is the problem with the truck wiring?

[ShadowFox]

Originally Posted by jesilvas

Hey, that pic looks familiar.
Trailer tow TRUCK harness connector
So what is the problem with the truck wiring?

I did read your thread before I posted this one, and if I remember correctly, I think I hotlinked the image from yours lol.

But the truck wiring is what I am trying to figure out. I borrowed a buddy of mine's trailer to tow my Mustang to the tuner after I build was complete. Well with the trailer plugged in, I wasnt getting any lights on the trailer, however the brakes charged.

So I grabbed my multitester and started testing connections on the 7 pin while the wife was inside the truck hitting the different functions. I received little to no readings on the 7 pin. So I went to AutoZone and bought that 7/4 pin harness that I linked above. The AutoZone piece came with a round connecter to plug into the truck's harness. Obviously this wont work. So I cut the round connecter off, cut the wires from the dead 7 pin to use its square plug. The colors for the wires were different, however I spliced the wires together as I thought they should go, and plugged it in to both a 7 pin trailer and a 4 pin trailer. The light results were the same on both trailers, partially working, however not as needed (right turn signal wouldnt work, left turn signal made both turn signals on the trailer flash, however independently of eachother, not as if they were hazards). I did find that if the break was applied on the truck, that all lights worked as intended.

This makes me believe taht there is an issue with the truck's wiring, and possibly a ground. I did buy the $100 replacement harness with the correct plug just to make sure I knew I wired the other piece right and received the same result. We did hook the 7 pin trailer up to another truck, and everything worked flawlessly.

[jesilvas]

Glad I could be of some assistance.
Well did you test the wires on the truck harness to see if they were working at all?
Cause maybe you just had a ton of fuses out.

[countryraised]

go to the fleet ford website, they have most of that stuff in the truck body builders layout book,
https://www.fleet.ford.com/truckbbas...1/maintoc.html
https://www.fleet.ford.com/truckbbas...l/2001/281.pdf

[ShadowFox]

Thank you for the link. I found my Chilton's book also that has the towing wiring information also. I am starting to think that this truck had a rough life before me. I have had to do the Marinco Mod because the block heater cord turned to dust. Parts of other wiring I have looked at on the truck I have had to replace. Looks like this will be my weekend project.

[ShadowFox]

I know its been a few months, but after towing my car to the track, I really got tired of the trailer lights not working. I pulled every fuse and found 3 blown. Replaced, and tada. I love easy solutions, but I hate it when im dumb lol