kramttocs Posted December 27, 2019 Share Posted December 27, 2019 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. Link to comment Share on other sites More sharing options...
grumpin Posted December 27, 2019 Share Posted December 27, 2019 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! Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 27, 2019 Share Posted December 27, 2019 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. Link to comment Share on other sites More sharing options...
kramttocs Posted December 27, 2019 Author Share Posted December 27, 2019 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. 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. Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 27, 2019 Share Posted December 27, 2019 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. 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: Link to comment Share on other sites More sharing options...
grumpin Posted December 27, 2019 Share Posted December 27, 2019 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. You should have trailer brake lights through the trailer connector from wires LG/O and O/LB. Link to comment Share on other sites More sharing options...
kramttocs Posted December 27, 2019 Author Share Posted December 27, 2019 You should have trailer brake lights through the trailer connector from wires LG/O and O/LB. 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. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 27, 2019 Share Posted December 27, 2019 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. Red/light green should be the ignition switch to coil wire. Link to comment Share on other sites More sharing options...
FuzzFace2 Posted December 27, 2019 Share Posted December 27, 2019 Red/light green should be the ignition switch to coil wire. 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 ---- Link to comment Share on other sites More sharing options...
grumpin Posted December 27, 2019 Share Posted December 27, 2019 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. I still think R/LG is when you use the controller to use the trailer brakes only, not pressing the truck brake pedal. Link to comment Share on other sites More sharing options...
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