After towing RV with bad batteries, truck blinkers...

Thank you

groundhogy wrote:
OP Update:
I think I have mostly figured this problem out.

It looks as if all of the back light grounds are routed to the one point. From the actual light bulbs, the ground wires pass through a connector, combine at a splice in the wire harnass, and one large ground wire emerges from the harnass and is bolted to the frame.

All three of these were getting old and were somewhat compromised but still worked before the towing incident. It looks as if the batteries of the TV and RV are directly connected upon plug-in. The bad batteries in the RV stressed this ground connection.

I was getting all kinds of 12 volts at the back lights.
I stuck a pin in one of the ground wires of a light bulb and touched the pin to the frame and the light came on.

I cleaned up the ground terminal and bolt, but the problem persisted.

Then I got the ohm meter out and found the splice. The splice was not working.
So I peeled off the tape and saw shrink tubing with weather goop around the splice. I cut all of this off.

This exposed one of these "modern" solutions. SOmehow they had four wires and they interleaved all of the strands together. Then they did a giant crimp action smashing it all into a little brick of wires. No solder or anything.

I have a 1949 Sylvania TV. Still works. All soldered.

So I heated that brick up and doused it with solder. Fixed.

Then the lights came on. But then the next day they went off again.
So I jiggled the connector and saw a light flicker.

Upon inspection, the ground pin of this connector was cooked. I cut it and it now temporarily has a wire nut on it.

I may just clip out this connector and solder all of the wires together.
This may also be the problem with the blinkers and back up light functions.

I saw evidence of heat damage to other pins as well.

:S

Oh shoot...

I forgot about that issue..

I never had it with the '03 or '06, but I do remember reading about hidden ground splices in the wiring harness on the early 2000's which would fail and cause lots of electrical gremlins.. Might have been on Ford Trucks Enthusiasts website..

Clip and solder, if you have it, heat shrink tubing that has built in glue that makes a weather proof good seal. Otherwise you can get spray "liquid tape" in a can and give it a couple of good coats and followup with some self healing/sealing rubberized tape.

On edit, somewhere in the 00-06 "F" series Ford integrated the BCM (Body Control Module) into the top of the fuse box located under the drivers side dash.

That location is directly under the windshield and the windshields in those model yrs often developed a hidden leak that would drip right onto the BCM.. Often causing the BCM to go nuts until it fails. When it fails, you have to replace not only the BCM but the fuse box since it is integrated. Those BCMs are difficult to find in working order so you might want to check under the dash to make sure you do not have a leaker windshield..

You might even wish to consider finding a way to make a splash shield to go over top of the BCM if you are planning to keep the truck for a long time..

OP Update:
I think I have mostly figured this problem out.

It looks as if all of the back light grounds are routed to the one point. From the actual light bulbs, the ground wires pass through a connector, combine at a splice in the wire harnass, and one large ground wire emerges from the harnass and is bolted to the frame.

All three of these were getting old and were somewhat compromised but still worked before the towing incident. It looks as if the batteries of the TV and RV are directly connected upon plug-in. The bad batteries in the RV stressed this ground connection.

I was getting all kinds of 12 volts at the back lights.
I stuck a pin in one of the ground wires of a light bulb and touched the pin to the frame and the light came on.

I cleaned up the ground terminal and bolt, but the problem persisted.

Then I got the ohm meter out and found the splice. The splice was not working.
So I peeled off the tape and saw shrink tubing with weather goop around the splice. I cut all of this off.

This exposed one of these "modern" solutions. SOmehow they had four wires and they interleaved all of the strands together. Then they did a giant crimp action smashing it all into a little brick of wires. No solder or anything.

I have a 1949 Sylvania TV. Still works. All soldered.

So I heated that brick up and doused it with solder. Fixed.

Then the lights came on. But then the next day they went off again.
So I jiggled the connector and saw a light flicker.

Upon inspection, the ground pin of this connector was cooked. I cut it and it now temporarily has a wire nut on it.

I may just clip out this connector and solder all of the wires together.
This may also be the problem with the blinkers and back up light functions.

I saw evidence of heat damage to other pins as well.

Thanks for the tips on the F-250 gdetrailer.
Yes, I have the same rusty issues as you do/did.
But I am now in Arizona, and my truck has thanked me as this has stopped it's rust from progressing.

Can you use your meter to determine if the fault is on the power side or the ground side? If power side, I think the wiring harness travels up the LH frame rail to the front and there should be a few inline connectors under the hood, above the LH front fender. Make sure these connectors are connected securely with no corrosion.

groundhogy wrote:
Im thinking melted something at this point, due to the fact that completely unrelated circuits are interacting.

But that is a great suggestion about the fuses.

'03 in PA?

Time to take a deep hard look at the wiring harness from the back all the way up to the front, it is possible you have a crushed or partially damaged wiring harness.

Check your bed crossmembers, good chance they are rotted out causing the bed to drop which can pinch the wiring harness..

I was lucky to have caught and repaired 3 of the front bed crossmembers that rusted out and were holding up the bed by the paint leftover that didn't fall off on my '03 F250..

Also a possibility of water intrusion damage to any wiring harness connectors from the rear all the way to the front on that same harness.

Vehicle lights not working correctly after towing may just be a coincidence as all of the trailer lighting wiring is completely isolated from the vehicles lighting via relays and separate fuses.

While you are digging around under your truck, inspect the fuel tank straps.. You are way overdue on those buggers as they rot out even faster than the rest of the truck.. Had a '06 that the back strap rusted out and dropped the tank, the filler hose was holding the tank in place :E .. Ford had spot recalls on the tank straps on F150s but not on F250-F350 in early 2000's :M

Take out all your running light bulbs and licence plate light, re insert one at a time until it happens, maybe wait a minute or two between replacing bulbs. Something has to give.

OP: Yes I'm still here. Thanks for the additional comments and thoughts.

On the grounds... The schematics i found show the lights grounded individually, but upon disassembling light fixtures, i found this not to be the case. I heard mention of a single ground causing similar problems.
F-250 2003. You lower the spare tire. THe ground is directly to port side of the spare tire winch on the inside of the frame. I cleaned it and it did nothing. But it was badly corroded.

The last couple days I have been trying to get the spare off. Ford has a security key on the spare winch to prevent theft. I didn't have the key (like a lug nut key), so I ended up using my dremmel to cut the wire rope that holds up the tire.

The flasher might be an easy one to try.
There seems to be a heating angle to this problem as if everything is cool, the flasher starts off correct speed, but increases with time.

I think next i will start with the night running lights and just get the voltmeter and do it the old fashioned way. Point by point working my way along the wire.

Here is another weird clue..
So looking at the schematic, there is the light switch that in running light position, allows 12vdc to flow to front running lights, rear running lights, and license plate lights.

Front running lights... fine.
License plate lights... fine (but dim and bright with blinkers).
Rear running lights.... off

If i can get some running lights, I will feel safer (from police) to drive at night. Right now the truck is completely black at night and I stick out like a sore thumb.

OP please come back and share the solution.

As mentioned flasher may be bad. They're cheap, truck is old, easy to replace, maybe time anyway.
But that doesn't account for no running lights or reverse lights.
Bad ground? Maybe but you said all lights grounded individually.
Wiring melted? Distinct possibility.
I'd start with the trailer plug in and work my way upstream. I think the early Powerstrokes were plug n play on the trailer plug from the main wiring harness to the tail lights. can you unplug that and eliminate it from the circuit?
Maybe take trailer plug apart and see if anything is loose, unhooked/touching another wire.

Good luck.

My last electrical fiasco was on my 86 GMC last year. Clean truck, pretty clean wiring, incorrect/intermittent dome/courtesy/cargo lights in cab. After spending far too much time on it, like 2 whole afternoons and coming up dry on any wiring issues, I discovered someone before me put the wrong style bulb in the cargo light!