Ok, cleaned up some "Scotch-Loc" wiring today, and replaced my trailer plug.

I need to ID 2 wires (maybe)

I found a section of the harness that went from my old (factory?) trailer plug (old-school 7-pin round like on a semi) to three very Ford OEM like connectors under the bed. Two 3-in and one 2-pin connector, running into the trailer plug.

Now, I have these figured out-
Green/orange- Right Turn
Orange/blue- Left Turn
Black (or Brown)- Tail/running lights
Big yellow- AUX Power
Blue- trailer brake
Grey- Ground

small red- was not hooked up
Black/red- Seemingly nothing, but was hooked up to the old connector.

What should the Black/Red do? Some trailer wiring guides I found online led me to believe it should be a 12v line, but it isn't. I've also been led to believe it could be a reverse light.

Is there a fuse for the trailer (I don't have any blown fuses, but I do have some blank spots on my fuse panel) it makes sense that there would be a fuse for a 12v wire running the length of the truck and into a trailer

The new 7-blade RV connector I just wired in today is working fine, but the last connection is supposed to be 12v and I don't have that yet. I don't want to run a new line if one of these is 12v and is just unhooked or has a missing fuse.

 

Your big yellow/aux power should be the same thing as your constant 12v to the trailer, shouldn't it???

Those colors must be some kind of weird ford wiring thing, as they don't quite match up to the standard trailer wiring colors.

Assuming your trailer plug was hooked into more plugs and it looks oem ford, you must have a "trailer special" tow package, which were either installed at the dealer where the truck was sold, or at the ford factory, or maybe both, (can't quite remember)

I would break out the test light if I were you and try to find out what the last few wires do.

BTW, what is your trailer plug grounded to? (you didn't list a color for the ground)
Have you tried plugging a trailer in yet?

 

The black/red may actually be pink/black, which is the reverse lights. Your yellow wire is a 12v feed. It has a fusible link at a junction block near the starter solenoid area on the passenger side fender. You should be able to follow the smaller wiring from the large bat terminal on the starter solenoid down till you find a bunch of yellow wires with rubber things in them called fusible links.

 

I got the yellow wire hooked up, it runs to the 2nd battery solenoid on the drivers side. I had dis-connected it years ago, (knowing THEN what it was for) because at the time, I wasn't using a trailer that needed it, and I hid it to "tidy up" my engine bay.

So thats hooked up and working, and my brake controler is working now too.

The black/red is most certainly not pink/black but if you meant black/pink maybe.

The connector I had on my truck before is the same one my grandfathers Volvo/Kenworth/Peterbuilts have for the trailer, and IIRC, those trailers have reverse lights, so a reverse line wouldn't be out of place. This could still be of use to me in the future, as I might need a reverse line for our next car trailer (something about a reversing solenoid to shut the brakes off while backing up I guess)

I still want to know what the RED wire is. It mostly boggles me, because it was unused in the old connector, and the old connector looks like a factory or dealer job. Most "previous owners" don't take the time to do that good a wiring job on trailer stuff.

 

Black/Pink = Camper and or Trailer Backup lamps.

Confirmed in the Factory Wiring diagrams for the 1985 F-series.

Red Wire: Camper Battery feed.

The Camper special wiring, and Trailer Special wiring is very simular. Very few differences according to the diagrams. So the red wire being unused on a trailer special makes sence. It's only used on Camper Specials.

 

The yellow is the 12v Aux line, and now, these aren't standard colors, they are Ford colors because they are in the trucks wiring harness, not the trailers. I went to town with my Power Probe 3 (a test light that tells the presence of ground, 12v, or anything in between with a built in meter)

The red and black/red wires I probed and found no voltage no matter what I turned on, but then again, I've been told my reverse lights are intermittent (I'll go look into that) so the black/red might have just not shown voltage because I have a bad TRS.

I have plugged the trailer in, lights all work (minus some bad bulbs) but the brakes don't. I know the line from the brake controller to the trailer is good, I suspect either a problem with the trailer or it's wiring, or the trailer brakes need three wires (12v, ground, and the blue signal from the brake controller). I'm wondering if the brakes need the 12v source too, and then maybe they'll work. As in the brakes use 12v and ground, and the signal from the brake controller doesn't power them, but merely "activates" them. I also have a low/dead break-away batter, because I don't have 12v to charge it.

Don't worry, for now the trailer is empty, and my truck is well more than capable of stopping it as is.

Thanks very much. I was beginning to suspect the black/pink was the reverse lights.

"The red wire"... argh, it's smaller than my factory speaker wire, so I doubt it's to charge the campers batteries. Unless I'm mistaken in my interpretation of what you're saying.

How can I tell if my truck has a trailer or tow package? Is there a code on a door tag or something like that?

 

The only way to tell for sure is the original window sticker, or the Build sheet.

You can get a copy of the build sheet from Ford. But it can take up to and longer than six months to arrive at your door. Well worth it for the information though. And it's free the last time I had one sent to me.

You can see the Red wire in this power distribution diagram here.

http://i447.photobucket.com/albums/q...l/scan0010.jpg

Circut 666, Red Wire: Exterior lighting: Camper Battery Feed.

There is also a Red wire going to the Trailer Brake Controller, Customer Use... Circut 284. This goes to the Trailer Brake Controller under the dash. This does not go beyond the cab or engine compartment though. Changes midroute from Circut 284: Red to Circut 37: Yellow at connector-1101 under the dash.

The diagram I do not have scanned, show circut 666: going to the back of the truck to connector 1014. From connector 1014 it goes to connector 1013. Connector 1013 is also used for trailer towing if equipped. It's one of Ford's cost saving measures%

 

If I follow this, you're suggesting that connector 1013 would be the furthest back and from there it would go directly to the trailer plug on the bumper right?

That last harness, going into the trailer plug, has all 8 wires in it, but it came with a 7 wire plug. I follow your reasoning, it probably was the same pigtail they used for a camper instead of a trailer...

Do you know where the red wire goes on the forward end? it says "Juntion block" is that the fuse panel in this case? I see a fusible link in the red wire, so I assume it doesn't go to the fuse panel.

I also have a single tiny red wire in my engine bay that's unhooked that goes to the alternator, I don't suppose that'd be the one do you? I need to buy the alternator harness from Green Sales, but I think that red wire was for the ammeter...

 

I edited my above post slightly...

According to the diagram, that is correct. They used the same pigtail connector and wiring for both in that section. Then they plugged in either the camper harness, that went to the camper, or the trailer harness that went to the bumper from there.

According to the diagram the junction block is connected to the starter motor relay, via a yellow wire and fuse lin

 

Yes, sloppy on my part I didn't look it up, was going by my memory. It is sometimes used for surge brakes. They are the type of trailer brakes that are hydraulic, and they have a master cylinder in the tongue of the trailer, and work when the weight of the trailer starts pushing on the tongue. Problem is when you try to back up, especially up a hill, it will lock the trailer brakes up, so they have a solenoid in the system that will lock the brakes out and this is activated by the reverse light power.



No. The brake controller drives the brakes directly. The brake controller varies the voltage to the brakes for different braking power levels, and the brakes are just magnetic coils in the brake assemblies. If you have a testlight, you can hook it directly to the blue brake wire, and fiddle with the controller and watch the bulb get dimmer and brighter with the different braking settings.

 

Wow, the edit feature screwed up both my posts above, sorry about that...

The junction block is on the passenger side fender close to the starter solenoid. It looks a little funky, and can be mistaken for aftermarket.

A Yellow wire goes to the junction block from the starter solenoid, to power the block. The rest of the wires bridge off the block from the junction block, including circut #666 if equipped.

Circut 284: Red also comes off the starter solenoid to power the brake controller, or off the yellow wire description above. The diagrams I posted show this much.

 

Not trying to hijack, but does anyone know the basic 4 flat wire connection? I do not think my trailer wires are tapped into correctly. In fact I know they are not correct.

Are there any plug and play connectors for 4 wire? My truck is an 83 carbed F-150.

I really hate cutting and splicing and would like to repair them correctly, 'cause I frequently pull a 4 x 8 trailer.

 

There is a plug and play kit for the 4 wire trailer lights for our trucks.

My 1981 has one installed at the dealer. It plugs into the connector between the frame rail and the rear harness. However I do not know if they are made anymore.

Go to Uhaul or a place that sells/rents trailers, tow hitches, and bumpers. See if they can order one for you still.