HELP flatbed wiring issues

[reed goodman]

Installed a hillsboro G1 flatbed on my 05 single cab. Cannot figure out the wiring and I'm wondering if i have more issues than being dumb. Here is what is happening-
I cut back the harness to the 8 wires that went to the original tail light harnesses. Tested all functions and I have everything correct other than reverse, which I get no hot signal for. Everything was fine before swapping the bed.
With the bed lighting (which are 3 wire leds) , ONLY the driver side brake light flashes when brakes applied, and the third brake light will no longer turn on, which did while trouble shooting. No fuses are blown.
Now, when i jam my test light into the butt connector, the trouble light will stop blinking and function correctly. When brakes are removed and applied again, the light then blinks again.

Lastly, the lights stay on for about a minute or two after switch is turned off. What is going on? Checked fuses, cleaned battery terminals, batteries are good (12.3 volts)

 

[Timd32]

Recheck fuse 38 it's shown as a 15A, shows in the integrated power module left front fender.

The wire for the backup lights is White / Light Green tracer.

All models show the Lower Left Side of the transmission has the reverse switch or range sensor, not sure on that just what it says, the power from the fuse is the White/Gray and the switch leg is the White/LT Green.

Then they all have a ground circuit Black wire off the lights.

The other lights look to run off of Fuse 15 which is shown as 50A.

 

[Yo Hoot]

Check all ground connections even not part of your change.

 

[reed goodman]

I have checked both fuses, along with the others and they are all good. Maybe it’s a coincidence and the third brake light bulb went out, will check tonight. Not sure why I’m not getting power to the back of the truck with the reverse wire though. When tested, I have 3 hots with brakes applied, which wouldn’t be the third brake light I wouldn’t imagine. I’ll check the trans sensor for power also.
Ordered some resistors for the lights so hopefully that helps with the weird blink with brakes applied and maybe the lights staying on. Maybe the test light draws just enough to shut the blink off.
It seems like more of a bad ground somewhere but everything is factory. Even retied the cab to factory bed ground to flatbed.

I could test the brake switch or replace it for $15 or so, but the main puzzling part is where’s my reverse hot wire? The color is there, but it comes on with the brakes!

 

[BigPapa]

Exactly what 2005 truck is it?

 

[reed goodman]

Exactly what 2005 truck is it?

long bed 5.9 48re 4x4 2500 single cab long bed
Manufactured early June 05

 

[BigPapa]

 

[reed goodman]

Here’s what I tried this time-
Tested trans range sensor- far left pinned hot in reverse. It was also full of oil… still no signal at rear of harness.
Ran a ground from battery all the way to the rear of the harness, that did nothing.

also, on the side of the drivers battery box I found this. The relay was unplugged, has a 15a fuse in it and the purple wire run up to the led headlights, which previous owner installed. Relay unplugged or not, makes no difference. Relay does work, not sure why it was unplugged.

that’s all I can think of messing with today, gonna have to wait and see if the resistors help at all.

 

[Timd32]

I know it's a mess of wiring. It's kinda all over the place so recheck the ground locations and splices again.

But from the range switch the splice is in the engine compartment then back to the rear.

You probably have to dig up that location.

The ground was/appears to come from under the battery area, but look at the pdf and see that again. One is shown and one is not, my guess is they are the same location.

The 3rd brake light is a separate fuse #24 this time, it's a 15A, then runs to the brake switch to the headliner splice location to the light, there is a ground for that in a complete different location. Looks to have nothing to with the reverse circuit.

The splices in these harnesses can be suspect at times for sure were not always perfect.

Here is some pdf information overload because its so many different circuits, find the S### in the list, or the G### in the list and it will reference the diagrams. I pulled all the S and G locations I could see that apply to the Reverse and 3rd brake light.

Something is either messed up under the hood at that S120 for the reverse lights or at the rear it was cut mid harness? Hard to say.

But I know my 96 can be a struggle it's not as shiny as the diagrams make it out to be, but they are pretty good to work from.

Good luck. I'm amazed it attached the 10 files...

 

[reed goodman]

Since I’m unfamiliar with all this electrical, can someone tell me how the range switch functions? In park, the plug has no current to it. In reverse, one pin does. Which pin goes to the reverse lights? Maybe I can jump pins and test it. I don’t want to cause more nightmares than I already have but I’m assuming an oil filled electrical connection should be replaced

 

[BigPapa]

If you look at the first diagram I posted, the power to the Range Sensor is on pin #1 and when it’s in reverse power is on pin #4.

 

[reed goodman]

Thanks for clearing it up and for all the help. I will jump the pins and see what happens, hopefully it’s just a bad switch. I’ll report back with the resistors installed which should be in tomorrow. I only know enough to get me in trouble and too stubborn to pay someone.

 

[reed goodman]

View attachment 132724 Found the reverse wire, it was hiding in the loom going to the trailer harness. There’s a white/tan wire in the rear left corner of frame that comes on with brakes and I’m having a hard time finding in a diagram what it’s for.
The third brake light was a bad bulb.

 

[reed goodman]

Here’s the wire

 

[BigPapa]

Sorry, but have you really looked at the diagrams I posted? There are Wht/Tan wires in the 2nd and 3rd diagrams.
One runs from the brake light switch to a splice on the left side of the steering column then to the high mount brake light.
One runs from the cluster to the cargo lamps in the high mount brake light.
One runs from the splice on the left side of the column to a splice at the center rear of the engine bay that says it’s for an aftermarket high mount brake light then on to the trailer brake controller.

 

[Timd32]

That will work, just to recap to maybe help make sense of what you have there here is a quick run down on how this kinda works so it could help in running down other issues.

Reverse Circuit

Somewhere along that back left frame rail is S325 that has 5 of those White w/Green tracers together.

The splices S### as shown in the diagram allow for "less" harnesses, it would be even more of a mess to run these wires all spiderweb out. It's always a mess and these can be pretty rough when cold outside to figure it all out.

So for this reverse circuit the Hot wire (White/Gray) from the fuse and the switch leg (White/Grn) run in the same bundle to the switch on the trans from the left side of the engine compartment area.

White/Gray down and White/Green back. White/Gray Hot all the time, White/Green Hot in reverse.

When the White/Green gets back to the left side of the engine compartment it meets its friends at S120 and there should be upto 4 of these same wires there in a splice.

1- FROM TRANS SWITCH
2- TO MIRRORS CIRCUIT
3- TO INTERGRATED POWER MODULE
4- FEED TO SPLICE S325 REAR FRAME RAIL

Splice S325 should now have 5 wires, one is the main feed and 4 go out and about to the various locations shown.

1- WIRE FROM SPLICE S120
2- LEFT REAR REVERSE SIGNAL
3- RIGHT REAR REVERSE SIGNAL
4- TRAILER HARNESS
5- SAYS "TAPED TOGETHER"

You have what I listed as wire #4 of S325 and I can see a second White/Green in the pic to the right.

Good work searching these down, if you get a better understanding of the harnesses and colors it helps out alot to then try to trouble shoot what is missing and why.

 

[reed goodman]

It’s definitely not easy being color blind and doing this lol

I’ve narrowed it down to that one wire without a home. I never cut back the stock trailer wiring harness, only the one to the tail lights.

other than that, issues are blinking brake lights but the wire has a steady signal and the leds staying on (dim) for a minute or two after lights are off.

I wired light green wire to brake light as the diagrams say, so with that said, the extra tan/orange wire must be the “high mount brake light”, but why is it run all the way back? Might just cap it off then I guess

 

[Timd32]

Yeah that's also good info for us to have as well. It's not easy for me for sure, but you got thru it.

One wire out of that Reverse splice will not have a home, says its just got tape on it, it's probably an upfitter wire for a custom build, ambulance or something, not sure. And I'm none of my trailers have reverse lights so I was surprised to see that's in that harness as well.

I wonder if there there is feed back from the Intergrated Power Module? somehow and you are bleeding down a capacitor circuit or something where the normal incandescent bulb has a different burden then the LED.

LED in general have a very low threshold to light up. Kinda like when you unplug a laptop charger and the lite is still on for a while till it all dissipates.

Are all parking lights on for 2min after shutdown. The fronts? Or just the bed lights.

I would set a stop watch and time it for sure and see what it works out to be time wise.

Maybe it's some sort of approach lighting circuit keeping the relay pulled in for the parking lights?

To test something like that you could pull say fuse 34 and you will loose just the Left side parking lights, if they stay or come on during this shutdown issue, you know it's from another circuit. Atleast you eliminated a circuit.

Pull up on your brake pedal maybe that's keeping the brake switch closed. I think you might have replaced that already.

 

[BigPapa]

Some trailers with surge brakes, typically boat trailers, use the reverse signal to de-activate the surge brake when backing up. Without it, you can't back the trailer up an incline.

 

[reed goodman]

The extra wire is a brake wire, not reverse. And yes, just the bed lights stay on after turning off the light switch. Have not swapped out the brake switch yet but that may be something I will have to do.
Spoke to an installer for Hillsboro beds and he said he has run into the issue of flashing brake lights and installed resistors at the lights to solve it. I have 4 resistors waiting for me at home and another two on the way for the headache rack turn signals. We will see how it goes…

to add, I cut back the harness to just after it tees off to the trailer plug, and the reverse wires were spliced for each side in the trailer harness fyi. I’ll post pics of that when I get home and mess with it in case anybody else comes across this thread with the same issues.