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Hello, have a quick question. I bought a 2018 F550 new and it has developed a problem with the constant power circuit that supplies the inside LEDs for the service body. Both Ford and the Upfitter say it's the others problem and want to charge us 100s of dollars to attempt to find the problem.
The constant power wire in the service body is dead. Zero volts. We can trace the wire until roughly the rear axle then it becomes too difficult to follow in the looms. We checked every circuit in the fuse blocks for continuity and also pulled every single fuse and check them as well. Everything is on. So we surmise there is a broken connection. Does anyone know what wire Knapheide and/or Ford would supply and use for this purpose? A color or a specific circuit that we should be looking for? Thanks.
There have been many issues with wires being pinched between the frame rails and the cab or truck bed. I believe there is a youtube video regarding the subject. Try blousing this site. The guy is a top rate Ford diesel tech.
There have been many issues with wires being pinched between the frame rails and the cab or truck bed. I believe there is a youtube video regarding the subject. Try blousing this site. The guy is a top rate Ford diesel tech.
Thanks. I did a quick search on this forum and nothing came up. I also sifted thru the above YouTube videos and didn't see anything. I am not even sure what to search for. Broken chassis wires, pinched chassis wires, service body wiring? In the factory wiring diagram manual it shows many circuits that are " customer" access but I don't even know if that what they would have used.
Hello, have a quick question. I bought a 2018 F550 new and it has developed a problem with the constant power circuit that supplies the inside LEDs for the service body. Both Ford and the Upfitter say it's the others problem and want to charge us 100s of dollars to attempt to find the problem.
The constant power wire in the service body is dead. Zero volts. We can trace the wire until roughly the rear axle then it becomes too difficult to follow in the looms. We checked every circuit in the fuse blocks for continuity and also pulled every single fuse and check them as well. Everything is on. So we surmise there is a broken connection. Does anyone know what wire Knapheide and/or Ford would supply and use for this purpose? A color or a specific circuit that we should be looking for? Thanks.
dID U CHECK WITH kNAPHEIDE? I AM SURE THEY USE THE SAME WIRE OR WIRES TO CONNECT WITH THIER BODIES RIGHT??
On our 3 550's with flat beds, they (Knapheide) tied into the "tow" wires. I'm not aware of any hot wires other then that being back there. Of course, we don't need any hot wire for anything other then battery charging on trailers.
On our 650's, it's the same way with our Boxes (different providers) for interior lights. The only other hot is for the lift gate, and that has heavy wire for the pump going to the batteries.
Have you checked the hot in the trailer plug, 550 don't normally come with tail lights, or trailer plugs. My bet/guess is they tied into this.
Look on rear, driver side, just inside the frame rail.
The only issue I've ever had with wires back there was the water separator shorting out.(Often driving in deep water)
On our 3 550's with flat beds, they (Knapheide) tied into the "tow" wires. I'm not aware of any hot wires other then that being back there. Of course, we don't need any hot wire for anything other then battery charging on trailers.
On our 650's, it's the same way with our Boxes (different providers) for interior lights. The only other hot is for the lift gate, and that has heavy wire for the pump going to the batteries.
Have you checked the hot in the trailer plug, 550 don't normally come with tail lights, or trailer plugs. My bet/guess is they tied into this.
Look on rear, driver side, just inside the frame rail.
The only issue I've ever had with wires back there was the water separator shorting out.(Often driving in deep water)
This exactly what I am looking for. I will investigate that hot wire tomorrow. Thank you very much for the idea.
I installed the wiring junction box shown in the photo below before driving the bare chassis cab (2019 F-550) to the body company for the upfit, as I wanted a clean and clearly defined break between Ford wiring and upfit wiring.
The upper left hand harness entrance to the box has a label. Look for this harness label when inspecting the wiring on the rearmost cross-member of your 2018 F-550. It will have the color codes and circuit identification for all wires in that harness.
The other three harnesses into the box (lower left, plus upper and lower right) were all added, as branches from the terminal posts in the box, that the Ford harness (upper left) serves.
The hot battery charge wire is Orange.
If the service box lights are tied in with the interior dome light, then the trailer wiring harness is not likely to be relevant.
I installed the wiring junction box shown in the photo below before driving the bare chassis cab (2019 F-550) to the body company for the upfit, as I wanted a clean and clearly defined break between Ford wiring and upfit wiring.
The upper left hand harness entrance to the box has a label. Look for this harness label when inspecting the wiring on the rearmost cross-member of your 2018 F-550. It will have the color codes and circuit identification for all wires in that harness.
The other three harnesses into the box (lower left, plus upper and lower right) were all added, as branches from the terminal posts in the box, that the Ford harness (upper left) serves.
The hot battery charge wire is Orange.
If the service box lights are tied in with the interior dome light, then the trailer wiring harness is not likely to be relevant.
.
This is also extremely helpful. There is a giant mess of wiring under the center bumper where all of the upfit wiring connects to the factory wiring. Where did you get that junction box? Thanks.
The 10 way circuit splicing box above is made by Pollak. Similar offerings by Pollak include 7 way post as well as a 7 way self resetting circuit breaker model.
On another F-550, I mounted a 12 way splice box...
I don't remember the specific brand of this 12 way box, but the point is that there is more than one type or brand out there to chose from.
Using search terms like "trailer" "circuit" "junction box" in various combinations will likely yield a selection from vendors you already may feel comfortable with.
We finally just called Knapheide today and they helped us locate the problem. There is an independent loom that goes from the front of the truck to the back of truck.(It can be zipped tied to the main truck loom) In our case the loom carries wires for strobes and interior service body lights. It terminates to the Knapheide service body wiring under the trailer hitch. We removed all of the loom covering and found a shrinked tube terminal that had corroded in half. Once that was cut out and new connection installed, the lights came back to life.
04-11-2021, 03:56 PM
