[tegwj]

I recently installed the UHaul hitch on my 2007 EX AWD. I also purchased the T-One 118465 from etrailer.com. Got it installed fine at both ends and plugged in the trailer to test.

Running lights work fine on all 4 corners plus side markers. Turn signal and brakes work fine on the passenger (right) side, but do nothing on the driver's/left, whether or not the running lights are turned on.

I called etrailer and they sent me a second 118465 which arrived today. I swapped out both the under-dash unit and the harness in the cargo area, but got identical behavior on the trailer.

I checked the contacts are clean, and obviously the bulbs are fine because they turn on nice and bright when the running lights are engaged. So I'm a bit stumped.

I can send back both units for a refund and buy the Honda harness but I wanted to see if there was anything else I should test beforehand. Any ideas?

thanks,
twj

 

[nacranym]

things you could do:
disconnect the trailer and check the signals appearing at the connector. you should see steady 12V for the tail and intermittent 12V for the left and intermittent 12V for the right signals. if not, the connector isn't providing the right stuff.
try the trailer w/ another vehicle. if the lights don't work correctly, the problem is probably in the trailer.

if the problem is at the connector, then check w/ the eTrailer folks about their stuff.

 

[Yoda E SC]

check the output at your trailer connector with the trailer unhooked. white is always ground, yellow should be left stop/turn, brown is right stop and turn, and green is running lights. test them with a digital multimeter while the associated functions are activated in the truck. if they all look fine, move to the trailer, colors are the same, check them with a 9 volt battery, negative side to the white, then each of the other wires one at a time with the white still connected to the negative side.

 

[ApriliaGuy]

assuming the lights are working fine on the car....

sounds like a trailer problem to me.

As sugested....try testing each of the outputs from the car 1/2 of the wiring harness. I'm guess they will be fine.

Look for a broken wire to left (yellow) side. Maybe a ground. Prolly a broken/disconected trairer wire imho.

 

[tegwj]

The trailer is fine -- tested with a different tow vehicle and its own factory tow wiring. It's definitely an odd behavior. I sent another inquiry back to etrailer.com today so we'll see if they identify any other clever tricks.

I do need to try out the multimeter on the 4-wire plug coming out of the Element but I have a suspicion I'll get nothing on the yellow wire. My fear is that there's an internal fault somewhere on the vehicle harness, separate from the T-One adapter piece, and it will be challenging to isolate and repair. But we'll see.

twj

 

[ApriliaGuy]

The trailer is fine -- tested with a different tow vehicle and its own factory tow wiring.

My fear is that there's an internal fault somewhere on the vehicle harness, separate from the T-One adapter piece, and it will be challenging to isolate and repair.

I forgot to mention the bulb too...the turn/stop function uses a different filiment.

When did you check the trailer with a different tow vehicle? Same day/time....or a few days/weeks ago? Just sayin'.

If you don't have a multimeter/test light handy, in the meanwhile you could always just try hooking up the trailer but switch the left & right tail light bulbs.

If there is something wrong with the vehicle wiring it will prolly be covered under warrantee....unless you've got some higer miles on an '07.

 

[tegwj]

Ok so I went out and poked around on the trailer. It's just a very simple open utility trailer. I didn't have a battery handy so I tested resistance between each of the three light circuits and ground.

There is an intermittent infinite resistance on the yellow wire, which obviously points to a potential problem, but the more curious discovery was that there isn't a brown wire on the trailer -- that pin off the 4-pin harness has both a yellow and green wire spliced into it. I haven't unwrapped the harness to see where they rejoin the primary runs, but I did look at the rear light housings. There is definitely only a single wire running into them -- so they are only single-filament bulbs I believe.

The thing I still don't understand, given the above, is how I can get lovely bright running lights on the driver's side, yet no brake or turn pulse. The physical wiring is the same between the plug and the bulb. My only theory is there is a short between the green and yellow wires, but if that were the case I would expect both sides to blink when I turned right. Instead I get a right turn exactly as I should. I'm pretty sure there aren't any diodes in the harness.

I'm busy all day today so clearly more troubleshooting is required but won't be possible until tomorrow at the earliest. It shouldn't be too difficult to isolate the fault with a bit more testing, but there is definitely something odd going on.

In the end if I can't trace it I'll pick up a harbor freight light kit and just rewire it but that seems wasteful if there is a simple fault somewhere.

Thanks for the continued suggestions!
twj

 

[tegwj]

Resolution

Ok, confession time.

So I just debugged the problem correctly. In short:

1) it was a problem on the trailer
2) the bulbs *do* have two filaments
3) the yellow wire was not properly seated in the metal retaining tang in the light housing on that side. There was just one strand of copper still in there, and it was lightly corroded. I disassembled the housing, re-seated both wires, and lo and behold, everything worked again.

About the only accurate thing I observed earlier was the fact that the 4-wire plug on the trailer side does indeed *not* have a brown wire coming out of it -- the Running Lights pin feeds through the moulded rubber housing to both a green and a yellow wire.

However inspection on the wires going into the light housing revealed brown wires on each side. So somewhere inside all the wiring loom and electrical tape, there must be a splice onto the different wire.

So, my humble apologies to all who offered correct suggestions which I didn't take seriously enough based on my own faulty observations. Lesson learned!

twj

 

[ApriliaGuy]

So I just debugged the problem correctly...

Cool. :smile: