FIXED!!Anyone deal with U-Haul trucks??

DamageINC · February 12, 2010

Ok guys, apparently all of the U-haul vehicles are "assembled" by the same team, so the aftermarket rear wiring "should" be similar across the board for the most part.

I have a '99 F-350 with a goofy exterior lamkp issue. So.. when you use the RIGHT turn signals, both fron and rear lamps operate normally, except that they flash fast, like there's a burned out bulb. When you use the LEFT turn signal, the front and rear blink normally, and at normal speed. When you turn the headlamp switch on and power up the parking lamp circuit, the right turn signal still acts the same, and the left turn signal sticks "on" when used. It doesn't blink, the left turn signal lights just stay on.

I found that pin 4 on the BOO switch is getting 12V with the brake OFF and with the headlamp switch powering up the parking lamp circuit. As a result, when the headlamps are on, the rear lights are always illuminated as if you were on the brake pedal (except if you use the right side trn signal, and then it just flashes fast).

Somewhere, the parking lamp circuit is feeding power to the brake light/turn signal circuit, but because this thing is a MESS of aftermarket wires, I'm killing myself trying to trace circuits with no diagram. Also, I am trying to find C210 but can't seem to locate that fucker for the life of me, haha, there's no picture in the FMC diagrams for it's location and just a brief description of where it's at - and I don't see it in that area at all.

I have more info but at this time I just want to know if anyone has seen anything like this before I start getting buried in diagram-free diagnosis, lol.

Dave

DamageINC · February 12, 2010

OH! And also, when I unplug the trailer harness adapters at the rear of the vehicle, the 12 volt feed to pin 4 of the BOO switch goes away. HOWEVER, when using the turn signals, they flash fast in BOTH directions, even though all of the lamps work normally. So it's like once I remove the trailer harness adapter, the system works just fine with the exception that they flash too fast. But the tail lamps come on fine with the headlamps on, and the brake lamps illuminate properly with the brake applied/turn signals applied regardless of headlamp switch position. Cool, huh?

Dave

Aaron · February 12, 2010

Does it have LED brake/tails in it?

Sounds like you got a couple issues, but a !?@#%! ground is the first thing that comes to mind... or maybe some fucky wiring on the column that's chafed through?

DamageINC · February 12, 2010

Yes, it does have the LED style lights. The factory wiring SOMEWHERE taps into a new harness (I'm looking for where, still) that sends your brake/turn sig/park lamp signal to a little control box that then sends a new signal to the tail lamps. The LED lights were "wired" like a standard 3157 bulb, with one ground wire (going straight to the body), one power wire for the tail lamp circuit, and one wire for the brake/turn sig circuit. Both the tail lamp and brake/turn sig circuits are 12v circuits, but applying 12V to only the "brake" ckt will still make the whole light illuminate bright, as opposed to needing BOTH filaments in a 3157 bulb to be illuminated for that "extra bright" effect.

Dave

Aaron · February 13, 2010

I've looked down the flashing fast road before, is there a... i wanna call it a ballast resistor across the signal lead to ground somewhere? To simulate the load that a bulb would place on the circuit that an LED lamp does not?

Any cute little boxes under the chassis anywhere that the wiring goes to?

This sounds like a real nightmare.

You could always feed un-fused 12v power to the circuit in question, and look for the smoke leak. Posted Image

mchan68 · February 13, 2010

Aftermarket flasher.

cbriggs · February 13, 2010

Ya, i believe grote makes an LED approved flasher that will slow the flashing down, as for the other problem......

blown99 · February 14, 2010

Whenever I get problems like this, I spend a 1/2 hr looking for obvious problems, then I cut out all the old rat nest of wiring harnesses and start from scratch. We have no idea what the other person has done, what they have used and or why. You can spend more time trying to diagnose the problem that it takes to remake the system.

Keith Browning · February 14, 2010

You can spend more time trying to diagnose the problem that it takes to remake the system.

Excellent concept and one I sometimes insist on because quite often a body builder has someone wire up the lighting without any consideration to weatherizing connections. From using sealing shrink wrap to packing connectors with grease. I have ripped out and replaced many body harnesses here in NJ where sometimes there is more rock salt on the ground than snow!

Aaron · February 15, 2010

I agree with both of you guys, and have done that LOTS of times.

The last couple chip vans i worked on, had a junction box about 8' from the back of the truck, where the chassis wiring joined to the box-builder wiring.

There was a junction block, and from the yellow and green wires, to ground, was a separate resistor to simulate the load of an incandescent bulb. It looked like a ballast resistor from an ol shitbox Dodge.

Like you guys said, a LED flasher seems to be the right way to fly.

DamageINC · February 16, 2010

Haha sorry I forgot to get back to everyone on this one! This truck has the usual F-series Solid-State flasher relay, that has a tendency to go bad and cause all sorts of funky issues. After scratching my head and inspecting most all of the aftermarket wiring, finding nothing visually wrong, I went ahead and ordered up a relay.

Fixed PART of the problem.. the turn signals both operate at normal speeds, now. However, the unwanted 12V at pin 4 still exists with the trailer harness adapter attached to the rear harness, which means that the brake lights are ON when the headlamps/parking lamps are on too. Everything is fine with the harness unplugged, so I've ordered up a new harness as well.

I think that maybe the failed trailer harness aapter somehow caused the flasher relay to freak out and ended up creating another problem as a result. But there are definitely two separate issues with the same system on this one, hahaha. Gotta love it.

Dave

DamageINC · February 20, 2010

Well guys, it's fixed. My trailer harness came in today and the problem is gone.

This is the part that comes out of the back of the truck and plugs INTO your trailer harness for your trailer.

After dismantling the rubber casing for the old plug, I found that there's actually a small circuit board inside there and it had overheated, burning the board and creating a small cross-short from the taillamp circuit into the left side brake/turn signal circuit.

This cross short eventually cause the flasher relay to fail, which is why there were 2 separate issues with the same system.

This trailer harness setup appears to be uniform across the U-haul line, so if any of you run into any similar issues with a U-Haul, I'd suggest disconnecting the 2 connectors that plug into the foot-long trailer harness adapter and see if that doesn't clear up (or at least change) the concern!

Dave