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Discussion Starter #1
I bought a 2015 transit cargo van for a camper conversion. The 4 halogen cargo lights never come on. Not when I use the key fob or when I open side or rear doors. The guy I bought the van from said they worked for a time and then stopped, he didn’t elaborate. All fuses seem to be fine but I’m not sure I checked the right places. All 4 lights have power. I was reading that the dome lights have power all the time and the circuit is completed via the ground. Electrical is not my strong suit. Do I have a bad relay? I was hoping to move the rear door lights under my bed for rear storage lighting and for that reason I like the idea of a door switch. I know these lights have been talked about a lot but I couldn’t find any info that helped me with my problem.
 

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Have you tested the ground wire to make sure it's actually connected to ground? You can run a jumper to it and see if the lights work.
 

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And the wires AT the light show there is 12vdc positive and negative? If you use an idiot light tester, it comes on when checking the wires?
147947
 

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Oh, did someone replace the original bulbs with LED? They only work when put in with the correct polarity.
 

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Discussion Starter #6
And the wires AT the light show there is 12vdc positive and negative? If you use an idiot light tester, it comes on when checking the wires?
View attachment 147947
So that’s the only thing I’ve checked them with, the idiot light. It lights up at every light no matter if the door/s is open or closed. I tried running a piece of wire from the opposite/ground side of the light to a chassis ground and no change. I believe they all have oem halogen bulbs with intact filaments. My dash display reads side/rear door open. :unsure:
 

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If the idiot light turns on with the alligator clamp on the bulb housing NEG and the tip on the bulb housing POS; then the bulbs must be burned out!

If you're clipping the clamp on NEG elsewhere, not the wire coming into the housing or the fitting in the housing, then it looks like the NEG wire is not connecting. You're right in that the NEG is switched by the door plungers and the overhead cab switch, not the POS.

You can also use a jumper wire (or two) to test the bulbs, just to make sure they're working.

I wonder if in the process of the "conversion" the cargo light wiring got messed with, usually to add a kill switch. Are there any mystery switches? All the overhead wiring comes up the Driver A pillar and comes out of the front headliner to go along the top side. That's where I cut into my wiring harness to add a switch to control the overhead lights (switch itself is over by the slider door).
 
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Discussion Starter #8
924B72C2-C921-4361-A550-1B4F85F87A48.jpeg

I really am a idiot haha. The lights work, just bad bulbs! I assumed the bulbs worked because all the filaments looked intact! Anyway, thanks for the advice. I tested with new led lights and they work.

Now the question is, is it feasible to cut the wires where they come into the van from the back doors and wire them to my house battery so as to keep them on the door switch?
 

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Discussion Starter #9
So I exposed the main loom at the back before it splits to go down the rear pillar and across the top of the rear doors. I was hoping I could tap in there but wow, there’s a lot of wires!

I suppose I could leave it alone and just extend the wire from one of the rear lights to where I want the new light. I just like the idea of isolating all the rear camping stuff from the vans starter battery.
 

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You'd have to cut between the starter battery side and the lights, and that's under the dash, in the A pillar, or near the B pillar. Going from the back wouldn't isolate the starter battery. A cut-less way to do it would be to find which fuse it is under the dash, make sure that fuse is JUST the lights, and pull it. Wire up a male spade connector the size of one leg of the fuse, and then run your house power to that, plug it in where the fuse used to be. Best to add a fuse in-line just to be safe. So, the POS would go from your house batteries through a fuse and into the fuse block under the dash, in place of one side of the previous fuse. You'll know WHICH side based on whether the lights have power or not!
148040
 
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You'd have to cut between the starter battery side and the lights, and that's under the dash, in the A pillar, or near the B pillar. Going from the back wouldn't isolate the starter battery. A cut-less way to do it would be to find which fuse it is under the dash, make sure that fuse is JUST the lights, and pull it. Wire up a male spade connector the size of one leg of the fuse, and then run your house power to that, plug it in where the fuse used to be. Best to add a fuse in-line just to be safe. So, the POS would go from your house batteries through a fuse and into the fuse block under the dash, in place of one side of the previous fuse. You'll know WHICH side based on whether the lights have power or not!
Clever idea, my only concern is proving then negative condition that only the light power runs through circuit containing the fuse where the house battery is being fed. The wiring diagram would certainly be helpful (if correct:eek:). Oh and does anyone with a 2020 know the location of fuse that might be. I've gone through the owners manual three times and can't seem to find a cargo lamp fuse anywhere.
 

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In my 2015 wire harness, the front and rear cargo light wires split off from a shared pair just forward of the ceiling rib that the front set of lights is on. If you crack open that improbably large plastic housing for the harness, you can isolate the light wires by tracing them back from the first row. Cut 'em, cap the ones coming from the front, and splice in your house wires there.

The 2020 (cargo) may be different. I don't know if they continued with that 2x4" housing for a 1/2" diameter wire harness. As noted in the Transit Forum Lore, I cut my harness and routed the whole thing through the body cavity (also large) above the windows (or where windows would be), then through away the cumbersome plastic housing.

Some have noted that the color coding for the harness wiring has changed a bit over the years. It's a little painstaking, but you can physically look at the wiring going into each thing back there (brake light, turn signal, door sensor, door lock, etc) and write down the color code of the wires. I should do that, and share a wiring chart on the forum; others can add their model and year.
 

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In my 2015 wire harness, the front and rear cargo light wires split off from a shared pair just forward of the ceiling rib that the front set of lights is on. If you crack open that improbably large plastic housing for the harness, you can isolate the light wires by tracing them back from the first row. Cut 'em, cap the ones coming from the front, and splice in your house wires there.

The 2020 (cargo) may be different. I don't know if they continued with that 2x4" housing for a 1/2" diameter wire harness. As noted in the Transit Forum Lore, I cut my harness and routed the whole thing through the body cavity (also large) above the windows (or where windows would be), then through away the cumbersome plastic housing.

Some have noted that the color coding for the harness wiring has changed a bit over the years. It's a little painstaking, but you can physically look at the wiring going into each thing back there (brake light, turn signal, door sensor, door lock, etc) and write down the color code of the wires. I should do that, and share a wiring chart on the forum; others can add their model and year.
I'm not brave enough to cut into the factory harness. If the fuse is elusive, I'd probably just run new wires to run the cargo lights from the house system and leave the factory wiring as is. I have seen where people have been able to relocate the wiring harness inside the wall without cutting into it. Not sure if that will be needed in my case or not. Might just need to chuck the 2x4. Time will tell on that. Maybe when I get my van next week (yea!) the paper manual will have something on the fuses that the on line PDF doesn't. 🤞
 

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If you attach the house to the starting by sharing wires, you might as well be sharing needles, because there will be bleed-back.
 

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Discussion Starter #16
In my 2015 wire harness, the front and rear cargo light wires split off from a shared pair just forward of the ceiling rib that the front set of lights is on. If you crack open that improbably large plastic housing for the harness, you can isolate the light wires by tracing them back from the first row. Cut 'em, cap the ones coming from the front, and splice in your house wires there.

The 2020 (cargo) may be different. I don't know if they continued with that 2x4" housing for a 1/2" diameter wire harness. As noted in the Transit Forum Lore, I cut my harness and routed the whole thing through the body cavity (also large) above the windows (or where windows would be), then through away the cumbersome plastic housing.

Some have noted that the color coding for the harness wiring has changed a bit over the years. It's a little painstaking, but you can physically look at the wiring going into each thing back there (brake light, turn signal, door sensor, door lock, etc) and write down the color code of the wires. I should do that, and share a wiring chart on the forum; others can add their model and year.
This is more along the lines of what I envisioned, I just didn’t know where and which wires to isolate. I’ve already removed the massive plastic cover. I keep going back and forth on the idea of cutting and relocating the wires in the frame 😅
 

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I believe I unwrapped/cut the canvas tape and traced the wires back from the light. I had an advantage, a completely empty van with no panels or covers or anything.

REDACTED
 

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I found my original post on the topic, under a pseudonym of course.

 
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This is more along the lines of what I envisioned, I just didn’t know where and which wires to isolate. I’ve already removed the massive plastic cover. I keep going back and forth on the idea of cutting and relocating the wires in the frame 😅
There are several posts that show how to relocate the harness into the wall cavity without cutting it.
Here are two. I think there may be others

2020 Ford Transit Cargo Wire Harness Re-Route NO...

Relocated cargo van wiring into the body cavities
 

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Morer info from old posts:

#34 Oct 15, 2017

The split into forward and rear wires? It's about at the area between the first ceiling crossmember and the cab. Just follow the wire back from the first crossmember overhead lights toward the front of the cab. Look for where there is only one WH/blu wire instead of 2 or 3(?). There should be a "lump" where they splice the wires together. You want to split it between the cab and that lump.

From this oldy but goody thread:
 
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