Factory Trailer Wiring

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Factory Trailer Wiring

kramttocs
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This post was updated on .
Truck came with factory trailer wiring and I am trying to figure out the R/LG wire.
Here is what I have. The red is the text from the labels on the factory harness and the brake controller manual.



The PO had the R/LG wire unused and the Red wire on the brake controller was hooked up to the switch Brown spliced wire.

I am trying to figure out exactly what the R/LG wire does. If it said FROM instead of TO in the EVTM then I'd say hook it to the red wire on the brake controller and it would be the braking source instead of the spliced in wired on the switch.

Wouldn't expect the trailer option to still require the user to splice into the switch...

Looking in the EVTM I can't find R/LG anywhere but on the Trailer Option page. The connectors on the Trailer Options page haven't led me anywhere either.

(The truck isn't wired up enough to test power to anything)

Photo below from the EVTM for easy reference. Again, if the R/LG at the bottom left said FROM then I could see it as being the source for the brake controller and the splice at the switch could be removed/unused.

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

grumpin
This post was updated on .
Page 77 of the EVTM shows the wiring for the trailer option for the stop lamps.

I went down this road, my trailer wiring was messed up at the trailer plug. Different scenario, but hopefully this will help.

Edit: I am not sure why it shows two ways to the stop/brake lamps, different wording on different pages.

One thing I think I figured out is that mine has factory trailer option, but someone had replaced the controller, which didn’t work anymore.

I removed it as part of the wiring mess it had. If I need a trailer brake someday, reckon I’ll start over.

Edit again: After looking at it, my guess is that if you just use the trailer brakes the brake lights come on. I think I figured this out and forgot! Frustrating sometimes!
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Factory Trailer Wiring

85lebaront2
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In reply to this post by kramttocs
If you look at the underhood portion you will see a power stud that is L side on the firewall. There should be a fusible link with a yellow wire that goes to a connector, C1106, the red wire from that goes in through the firewall to C1101, a gray 3 pin connector (I believe it was a round female one on Darth) this is where the brake controller should connect. Ford used to sell a pigtail that plugged in to it for trailer brakes. The output from the controller (keep in mind when these trucks were built hydraulic controllers were the norm) goes back through C1101 then out through the firewall to C1102, and from there down the frame rail to C1110 on the rear crossmember.

The other trailer wiring is in the Turn/Stop & Hazard lamps section of the EVTM (pages 76-79) where the location of the rear connectors is pictured. Trailer running lights are in the exterior lamps section. If you are not hopelessly confused now, I believe I actually have a trailer tow chassis harness from Darth (crew cab long bed) that I saved when I rewired him to 1996 harnesses.
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Factory Trailer Wiring

kramttocs
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Thanks Bill. Correct -all that is there. I am just trying to figure out the R/LG that is on the pigtail under the dash. I can't find where it goes to in the EVTM.

Dane - definitely frustrating. Any reason for it other than to provide brake signal to the controller seems redundant like you said.

So you are thinking the trailer brake lights come on even with the R/LG disconnected?

I guess that is really the determining factor because that has been the assumption I have been making but if you look at it the other way then the book makes more sense. R/LG wouldn't show up anywhere else in the EVTM besides page 30 (in 1986) because that is the actual 7way trailer plug.

So still looking at it this way where the trailer brake lights don't work without R/LG connected and considering Bill's point about the hydraulic controllers then Ford was still requiring the owner to splice into the brake pedal switch. But with a hydraulic controller the splice would just feed the trailer brake lights. With an electronic controller the splice would need to feed both the trailer brake lights and the brake controller.
Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

85lebaront2
Administrator
The newer trucks have a 4 pin brake controller plug. Here is my "old fashioned" Kelsey-Hayes hydraulic controller.
Controller and 1996 adapter harness:.

Mount I made for the 1996 dash:

Controller wired up (ground really isn't needed):

Installed and plumbed:

Hydraulic line to 1993-97 master cylinder with cruise control override cancel switch:
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Factory Trailer Wiring

grumpin
In reply to this post by kramttocs
You should have trailer brake lights through the trailer connector from wires LG/O and O/LB.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Factory Trailer Wiring

kramttocs
Administrator
Definitely what page 77 looks like.
What is the 'chassis cab and flareside only' box beneath the 'trailer only' referring to?

If LG/O and O/LB are the brake lights also then we are back to the redundant R/LG wire

Even though I don't have power, I may do a continuity check today.
Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

Gary Lewis
Administrator
Red/light green should be the ignition switch to coil wire.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: Factory Trailer Wiring

FuzzFace2
From the sounds of it I am happy my truck does not have factory trailer wiring.

It's not hard to wire in a brake controller under the dash and run a 10ga blue wire down the frame rail the same time you run a 10ga red from battery to supply power to the travel trailer to charge batteries.

For trailer lights I have one of them Tee's that plugs in between the trucks frame harness and tail light harness. Being I will run head light relays the few lights going thru the head light switch is nothing now.
Dave ----
Dave G.
81 F100 flare side 300 six / AA OD / NP435 / 2.75 gear
http://cars.grantskingdom1.com/index.php/1980-Ford-F100?page=1
81 F100 style side 300 six/SROD parts truck -RIP
http://cars.grantskingdom1.com/index.php/1981-Ford-F100
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Re: Factory Trailer Wiring

grumpin
In reply to this post by kramttocs
I still think R/LG is when you use the controller to use the trailer brakes only, not pressing the truck brake pedal.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Factory Trailer Wiring

grumpin
In reply to this post by Gary Lewis
Gary Lewis wrote
Red/light green should be the ignition switch to coil wire.
Interesting that they’re the same color.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Factory Trailer Wiring

grumpin
In reply to this post by kramttocs
<quote author="kramttocs">
Definitely what page 77 looks like.
What is the 'chassis cab and flareside only' box beneath the 'trailer only' referring to? 

I believe that’s the difference in the drawing, chassis cab and flareside only, no trailer light option. Trailer only with the option.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Factory Trailer Wiring

85lebaront2
Administrator
In reply to this post by grumpin
On mine I believe the LG wire is the brake lights, I know I can "brake check" a clown who is dumb enough to put his little POS Jap or Korean crap on Darth's bumper by simply pushing the knob to the right. Red is power, Blue trailer brakes, White ground (not really needed on mine) Light Green is brake lights. FWIW, the 1992-97 PDC has two dedicated fuses for trailer stop and turn, they are slaved off the truck rear lights in the PDC. I went one better, due to previous experience and added two more relays, one for each side so a dead short in the trailer harness or trailer will only kill those circuits.
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Factory Trailer Wiring

kramttocs
Administrator
In reply to this post by grumpin
I get the trailer wiring is only with the Trailer Option but what is the chassis/flareside specific piece in the diagram that doesn't apply to stylesides (off topic likely but would like to know)?

So turns out for my truck that tracking down R/LG doesn't seem to matter. I started to do some continuity checks but after all of them failed I realized I hadn't routed and connected all the wiring under the booster
While I was by the rear bumper looking at the 7 way plug I notice up near all the connectors there was a R/LG wire with a female barrel connector not connected to anything.
I had actually dug dirt out of the connector and stuck a male plug in there to keep it clean right after I got the truck but had forgotten about that.
Looks like it's a second way for the lights as you said, Dane.
I'll let it go for now until I get power back in the truck and test it out.

Thanks all!

As a side note, did get the brake controller installed and will cover that in the build thread later tonight.
Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

kramttocs
Administrator
In reply to this post by 85lebaront2
Does that not also apply the trailer brakes?
Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

grumpin
In reply to this post by kramttocs
My bad! I was thinking styleside in my head, but that’s not what it says.

Well... now I’m curious!

Edit: Unless it’s for connectors C354 and C355.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona
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Re: Factory Trailer Wiring

85lebaront2
Administrator
In reply to this post by kramttocs
The Kelsey-Hayes hydraulic controller has two internal contacts, one simply turns on the brake lights and comes on with very little motion of the lever, the second is a variable resistance, the further the lever moves, the greater the applied voltage. The brake light contact makes before the brake magnet feed, also I use that when running without anything behind or with my Aluma open cargo trailer which does not have brakes. Purpose is to scare the clowns that like to tailgate thinking their 2000 lb Honduh or similar is going to intimidate me in a 6400 lb crew cab DRW truck.

Years ago, taking our oldest son to Atlanta to attend DeVry there, we were going down I-85 passing a long line of slower vehicles a Honduh got right on the back bumper, my wife asked "aren't you afraid he might hit us?" I informed her that if he did, the class 3 receiver hitch under the rear bumper of a roughly 5000 lb empty weight 1971 Colony Park wagon would do more damage to his car than he could think of doing to ours. After a few miles, I think the reality of the wagon tailgate being bigger than the front of his car and the facts that (a) I wasn't paying any attention to him and (b) was running 5 mph over the 75 mph speed limit he dropped back and just sort of drafted us till we passed the line, at which point I went back to the right lane.
Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Factory Trailer Wiring

kramttocs
Administrator
Thanks Bill. I've used the lever when testing the brakes but don't think I have when driving so was curious. The two contacts makes sense.
Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

kramttocs
Administrator
Here are the factory trailer wiring connectors.
Note that C1110 is a standalone harness that goes from under the brake booster (where it goes through a grommet into the cabin to connect to a brake controller) to the rear crossmember. This harness includes the black Trailer Lamps circuit from C1104.

Scott
'Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole

But there ain't nothin' wrong with the radio
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Re: Factory Trailer Wiring

Gary Lewis
Administrator
Good documentation.  Thanks, Scott.  
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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