U-Haul CT13 Taillights Issue: - Fiberglass RV

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Old 10-07-2017, 10:06 AM   #1
Senior Member
Name: Gary
Trailer: UHaul CT13
Posts: 266
U-Haul CT13 Taillights Issue:

Electrical Question:
Long ago now, I swapped my broken taillights for assemblies from a mid-80s GM pickup.
I've just revisited my camper wiring--the running lights/brakes/turn-lights side of things. Turns out my initial configuration wasn't working well at all.
Since I'm NOT an electrician... and since I'd used a 5-way connector instead of the more-common 4-way setup... I decided to forget about MAYBE wiring up the reverse lights someday, and just use that bulb for a separate running light.

SO--I popped out my pickup's taillight fixture, and spliced into that wiring for accessing power & grounds for the new 5-way harness... then took the Curt converter box that I'd added on the camper out of play... and re-wired the camper taillights.
So now there's a separate positive lead for L & R turn signals, brakes, running lights... and one for ground.

All light functions work great when tested individually. Bright lights. BUT--when I have the brakes on, the turn signals on the camper no longer flash. [these 2 functions are coming from a shared, 2-filament bulb] The turn lights DO continue to flash on the pickup during this situation [brake + turn].

Any thoughts?

P.S. I also removed the clear lens over what was the reverse light, and patched in a red lens from part of a damaged lens I had. Also substituted the reverse [now running light] bulb, as I thought it was over-bright for a running light. Was a 1156 [26-Watt]... now a 1003 [12-Watt]. Still plenty bright.
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"You'd care less what people think of you if you knew how seldom they did." E Roosevelt
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Old 10-07-2017, 10:16 AM   #2
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Name: bob
Trailer: Was A-Liner now 13f Scamp
Posts: 3,072

I gave up took the trailer to my mechanic in about 15ms he said you are ready to go. What I assumbed was ground was not I am not a trailer light guy.


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Old 10-07-2017, 10:46 AM   #3
Senior Member
Name: Gary
Trailer: UHaul CT13
Posts: 266
I sympathize. About ready to admit defeat here.

But I did get some decent response over on the U-Haul Facebook page, and did some further thinking, as follows............

I may have my error sorted, though I still don't understand how the juice flows.
BUT, here goes:
[1] Both pickup and camper have a 2-element bulb up top, and a separate single-element bulb below..
[2] But on the pickup the upper bulb handles running & brake functions, with lower bulb doing turn signals..... whereas on the camper, the upper bulb is wired to handle brake & turn, with the lower bulb doing running light. So I DON'T have the circuitry arranged the same between the pickup & camper!

[3] I don't understand how the electricity flows [or doesn't], but I'm guessing this is the problem. [repeat--"guessing"]
"You'd care less what people think of you if you knew how seldom they did." E Roosevelt
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Old 10-07-2017, 12:50 PM   #4
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Name: K C
Trailer: 1971 Trailswest Campster
Posts: 2,905
pictures are worth a thousand words. Do this: open your browser and paste in "trailer light wiring diagram". The choose the option for an image search.

You will then see color coded images that explain what the function of the various colors of wire in the harness are. I printed out copies of the diagrams to have in my hand while I was making the connections. I also have a copy of it stored on my tablet, computer file for my trailer project, trailer notes file on my phone etc. It is good to be prepared to make repairs while on the road.

Next get a label maker, very handy item to own, and create labels to wrap around the ends of the wires near your tail lights. One label on the piece coming out of the tail light and a second label to put onto the wire coming out of the tail light harness. You can also add a label around the wires where they enter into the trailer. That way if you ever need to change the tail light or replace a harness you won't be confused as to the function of that particular wire.

Our long and short term memories are not perfect so labels are worth taking the time to put onto wiring harnesses. If you ever go to sell it the next owner will certainly be appreciative of having those labels on the wires.

I am remodeling my trailer that I gutted and putting in all new wiring. As there are devices that were never part of the original setup I will put in labels on everything. I also add labels on the longer wiring runs in locations where those wires pass close to other wires that might split out of a bundle and head in a different direction. It makes things much easier to quickly identify the purpose of an individual wire should I ever need to trouble shoot a failed connection or device or splice in a second device. Fortunately building wire bundles, securing them and inspecting the installation of wire bundles on large commercial aircraft is part of my work history. So I know the value adding labels to make it easy to identify what the wires are is something I should do for my own convenience.
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Old 10-09-2017, 08:45 AM   #5
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vintageracer's Avatar
Name: To Infinity & Beyond!
Trailer: 1985 Uhaul VT-16 Vacationer, 1974 Hunter Compact II & 1977 Argosy 6.0 Minuet
Posts: 580
For those interested.

For the past year I have been working on a project to reproduce the Uhaul tailight lens. The original lenses are 2 piece yellow/red lenses. I tried to make these however it was difficult to separate the 2 piece lenses to make molds for each half. I ruined several good original lenses in pursuit of this solution to make an identical reproduction.

As such I have made a single cavity mold and am in production of a completely red lens. These lenses are just like the originals in that they are universal and work on the the driver's and passengers side of your Uhaul trailer.

Cost is $79.00 SHIPPED to the lower 48 United States of America with shipping to other locations base upon actual cost.

If you are interested in a set please contact me at strinich@comcast.net.

Due to the single cavity mold I am producing these lenses in batches of 10 lenses or 5 pair. Initially sold as pairs and singles may be available in the future however not at this time.

I look forward to hearing from you if you have an interest in replacement lenses for your Uhaul Trailer.

Please check out the Uhaul trailer Facebook page for anything and everything about Uhaul camper trailers.
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Remember "Drive Fast, Turn Heads, Break Hearts"!
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Old 10-09-2017, 10:42 AM   #6
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Name: Kevin
Trailer: 28' Bigfoot Silver Cloud
Woodstock, IL
Posts: 1,284
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Sounds like a great price for a pair of lenses! We no longer have a UHaul, but thanks for doing this.
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Old 10-15-2017, 12:18 PM   #7
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Joe MacDonald's Avatar
Trailer: Trillium
Posts: 903
you cant use the same bulb for brake and turn if you want separate functions, because they share a common ground it wont work right, you end up bridging both filaments in the bulb. the only way it might work would be to wire in a reverse converter as if you had separate orange signals. you could go back to the chevy original where the top bulb is marker/Brake, and the lower becomes signal. you may still need the convereter even with this configuration. the only way around is if your tow vehicle has a separate brake, signal, and marker output( this would take 4 of your 5 wires (left,right,brake,marker) leaving one wire for a ground.

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Old 10-15-2017, 02:15 PM   #8
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Name: bob
Trailer: Was A-Liner now 13f Scamp
Posts: 3,072

vintage racer how are you doing this? Did you have someone make the molds for you.

I am fascinated by this and you are amazing!! just so you know!

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Old 10-15-2017, 05:18 PM   #9
Senior Member
Name: Gary
Trailer: UHaul CT13
Posts: 266

Thanks for confirming the brake/turnlamp issue. It took me a while after wiring things up to realize that I hadn't arranged the camper lights to match the pickup's.
My plan at this point is to take the camper's light assemblies back out again and swap the leads going to turn & running lights. Then--as they are on the pickup--I'll have the 2-filament upper bulb on the camper used for running light + brake... and the lower, single-filament bulb as the turn-lamp.........as it is on the pickup.

That will still leave me with a non-standard setup, but one that should work fine with my own tow vehicle[s]. If I should ever sell the camper, I'd probably feel like I had to "normalize" it at that point.

"You'd care less what people think of you if you knew how seldom they did." E Roosevelt
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light, lights, u-haul

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