Factory Trailer Harness?

[pastorjeep]

I need some help here. 89 F250 7.3, ZF5, and factory tow package. So it has the two four pin connectors located at the rear to go to a seven pin plug. I have no power at these pugs but all normal truck features function correctly. What route does the factory harness connectors take? Why do I have brake, reverse, turn lights but nothing at these connectors? I just wired up a new seven pin plug using the old ford color codes crossed over to SAE.

 

[franklin2]

The whole idea is to have the trailer on a separate circuit from the truck with separate fuses. So if something bad happens at the trailer the truck lights will still work.

You have to be a detective, or have the proper literature to hunt down these other circuits. If they were never hooked up since new, you will probably find fuses missing. Another problem, it seems Ford changed the trailer circuitry almost every year. So sometimes you will find a little special fuse box under the hood in various places with the trailer fuses and relays, sometimes it's in the underhood fuse box if you have one. You should also have some wires hanging down under the dash with a weird plug for the brake controller. If you look hard enough, you may still be able to find the adapter that fits the Ford plug, and gives you blunt cut wires that you splice into your aftermarket controller.

 

[OLDBULL8]

On a tow package, there should be a Blue and a Orange or Red wires wrapped up in the harness at the rear and in the harness by the firewall. The Blue is the 12 VDC brake power, the Red or Orange is the trailer battery 12 VDC charge wire. Normally you have to get a TEE pigtail connector for the Brake/Turn signal lights (Green for right, Yellow for Left could be Vise Versa) and a Brown wire for the trailer running lights. A white wire from the 7-pin has to be hooked to the frame for a ground.

I have no idea why there is two 4 pin connectors at the rear.

Can't recall what year Ford put a brake controller connector under the dash close to the center, if there is one, you have to get a Ford pigtail to hook up the controller. Also if there is one, there will be a relay under the hood hanging by the firewall.

If you have the connector under the dash and can't find a pigtail for it at an RV store, I still have a couple.

If you don't have the connector under the dash, it's a whole new ball game for a hook up. Have to know.

 

[pastorjeep]

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This what I have at the rear of my truck but they have no power going to them. (this is from a thread on FTE http://www.ford-trucks.com/forums/1164906-factory-trailer-wiring-harness.html

 

[OLDBULL8]

Someone rigged up that so they could probably use it for 2 different trailers, one with brakes, one without. Your gonna have to find out where all the wires go up front.

#1 plug has the Blue (Brakes) - Orange/Red (Battery) - Black ? These wires have to go up front someplace.

#2 plug, Green ( Right Brake/Turn) - Yellow (Left Brake/Turn) - Brown ( Marker/Running/Tail/License) - White (Neg/Ground) These wires could go to a Tee connector in the rear.

https://www.google.com/search?q=tra...=IcTBV5vdF8bzmAGNqoOoDA#imgrc=9ehkCIQ7317LhM:

 

[pastorjeep]

These are the factory tow package plugs. They have twins up under the hood that are not attached to anything? So basically I need to just tap into the bed harness for lights, brakes, blinkers and then run a white to frame ground, and a 12v key on, and then wire in a aftermarket brake controller? My sig truck just had a T in the bed harness. But this 89 with factory tow doesn't have the same type of plug.

 

[laserjock]

My 91 had a t connector that they used for the tail lights. It may just be hiding up in there deeper.

 

[OLDBULL8]

I'll guarantee you that is not a factory hookup, Ford would never put such a fu*** up rigging on a truck like that.

 

[cpdenton]

I'll guarantee you that is not a factory hookup, Ford would never put such a fu*** up rigging on a truck like that.

My truck has it.....and the truck I took my factory 7 wire trailer connector from had it as well.....

 

[cpdenton]

Here is a picture of the two connectors.

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And here is what the connect to.

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[OLDBULL8]

That's a new one on me. I was in the RV service business from 89 to 2004, put lots of hook ups on Fords and never seen anything like that. Live and learn. But I'm too damn old for that now.

 

[pastorjeep]

Yep it's factory. Got mine up and running, tried it with the 33 footer today and everything is a go. The old style ford relay under the hood just needed some coaxing.

 

[pastorjeep]

Hey CP, I wired in an aftermarket seven pin plug to the wires, but I have a question maybe you can answer. On the larger plug you should have a light blue with black stripe (brake control) and a red with light green stripe that the factory service manual calls "trailer brake stop lamps". What location on the seven pin plug does your r/lg terminate at? I just left mine taped up right now because everything is working and I couldn't figure where the eighth wire went.

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