Trailer lights troubleshooting help

[abajus]

I'm wondering if someone can help me trouble shoot an issue with my trailer lights. I've got an old Alumacraft fishing boat on an old trailer. The lights are similar to if not these exact ones https://www.etrailer.com/Trailer-Lights/Optronics/TL5RK.html. Last year I replaced the whole left tail light as it was smashed with the exact one that was there before and everything worked. This year, Right trailer light was out. Everything else worked. I swapped the bulb. Was checking lights with the truck. They were on, signals worked, brakes worked except right one didn’t get brighter when pressing brake. Asked buddy to press again. Then the whole trailer went out and hasn’t worked since.

Fuses in truck are fine. I’m getting current at the linkage. (I've got a converter that changes it from 7 pin to 5 pin and it lights up when plugged in)

Thought it might be the ground wire by linkage so I sanded it to bare metal put dielectric grease on it. Still doesn’t work.

The left tail light I installed last year has ground wire installed. Right one (old preexisting) does not have a ground wire on it. I don't know if the previous owner cut it off. IT worked fine without one and even with the bulb out until I tested it.

I matched the bulb I bought to the closest similar one I could find as it was really old so I don't know if it could be that bulb? However I don't know why that would cause all the trailer lights to go out.

Some help would be much appreciated. Thank you!!

 

[jimmbo]

"Similar Bulb"? A lot of Trailer Lights used 1157 bulbs. Take that new bulb out and see if the remaining lights are again working

 

[abajus]

"Similar Bulb"? A lot of Trailer Lights used 1157 bulbs. Take that new bulb out and see if the remaining lights are again working

I'll give that a shot tonight

 

[briangcc]

Are you sure your truck fuses are fine? Cause from your description a fuse blew if the entire trailer went dark.

IF I didn't know better, your trailer wiring probably had a short in it somewhere. Toyota mechanic is still baffled I blew a 30A fuse in the Tundra when my trailer shorted. Lost all my marker lights on the Tundra and trailer. You might want to reconfirm that all your lights are working on the tow vehicle.

Other issue may be that some trailer manufacturers rely on the trailer coupler-to-ball connection to provide a ground. That gets rusty/dirty the lights go a bit wonky. For testing only, hook a jumper cable to a good ground on your tow vehicle then the frame of the trailer. See if when the trailer plug is connected, you have lights.

 

[abajus]

Are you sure your truck fuses are fine? Cause from your description a fuse blew if the entire trailer went dark.

IF I didn't know better, your trailer wiring probably had a short in it somewhere. Toyota mechanic is still baffled I blew a 30A fuse in the Tundra when my trailer shorted. Lost all my marker lights on the Tundra and trailer. You might want to reconfirm that all your lights are working on the tow vehicle.

Other issue may be that some trailer manufacturers rely on the trailer coupler-to-ball connection to provide a ground. That gets rusty/dirty the lights go a bit wonky. For testing only, hook a jumper cable to a good ground on your tow vehicle then the frame of the trailer. See if when the trailer plug is connected, you have lights.

Yeah, I checked the fuses both for tail lights and the brake lights on the tow package and they work. The linkage that takes it from 7 pin to 5 pin lights up as well meaning theres power. I'll try the ground test as well. I just backed my truck up and connected the lights but not the ball.

 

[jimmbo]

Since you didn't put the Trailer on the Ball, you might not have a ground, often the ground wire to the Tow Vehicle breaks but the Lights still work, cause it is using the Hitch to complete the Circuit. 50 yrs ago my Dad never used a 4 pin connecter for trailer wiring, He used the 3 Prang Prong(common Cord connectors) and used the hitch for the ground.

 

[abajus]

Ok so this is what I tried tonight:
1) hooked up trailer on ball to see if it would ground. No lights.
2) rechecked all of the fuses (towing signals, towing brakes, towing lights) all are fine - see picture below. No lights.
3) Double checked ground area for corrosion, put more dielectric grease. No lights.
4) took out the light bulb I replaced (which ended up being a 1157 silverstar bright light. No lights.
4) tried to check trailer lights with a 12V battery. No lights.
5) inspected wires along entire trailer for kinks or wearing or breaks. Found nothing.The wires were actually in fantastic shape.

Any other thoughts?

 

[jhande]

That ground connection you cleaned, was it on tow vehicle or trailer?
I'll assume on the trailer. Are 2 wires attached to that ring connector (should be one for each light socket)? Or is that coming from the trailer plug going to trailer frame? If the later then your lights are grounded through the trailer.
Pick up a cheap circuit tester/test light such as this one - click here.
7 pin to 5 pin convert, sure it's not a 4 pin not a 5?
I'll assume 4 pin. Wiring coming out of plug connector - 1 wire for ground. 1 wire for running lights both sides. 1 wire for left turn/brake light. 1 wire for right turn/brake light.
Using the circuit tester start by testing the female connector on the tow vehicle (ground alligator clip to vehicle) just to verify proper function. If all works fine next...
Plugin male trailer connector and poke the tip of tester into the wires one by one just behind the plug. If all works fine next...
Remove light bulbs and CAREFULLY insert tester tip to touch JUST a contact point in the socket. WARNING: Don't touch the side of the socket or both contacts at the same time or you'll blow a fuse.
I'm going to take a shot in the dark and if all worked fine until testing the sockets you have a bad ground somewhere. I don't like grounding through the trailer, I prefer an actual ground wire from the plug to light socket.

 

[roscoe]

Use a tester or volt meter and test the pins in the 7 pin socket on the truck.
(don't trust that light on the converter)

If good, then test the pins on the output of the converter the 4 or 5 pin side.

If good, the issue is the trailer.

Are all lights on the trailer incandescent? or is the one or more an LED?
You don't have these do you?

SYLVANIA ZEVO 1157 White LED Bulb​

 

[Grub54891]

I run the grounds to each and every light. You can’t trust the the trailer to complete the grounds.

 

[abajus]

Sorry for any confusion, it is a 4 pin harness and that picture is the ground at the harness. I think I've found the issue. I was taking off the clearance light cover and removing the bulbs in each of them to check for an overload scenario. One of the lights, the metal plate that the bulb makes contact with fell out as soon as I took the cover off and the sockets were extremely corroded. I also noticed that the wire going to this wasn't in good shape. When I followed it back to the splice the yellow wire at the splice was also open and corroded so I'm assuming this is where it's shorting. Theres a pretty good sale on an LED kit right now. Rather than risking the same issue somewhere else after putting the time into fixing this, I'm gonna redo the whole thing. Thanks so much for your help, I've learned a lot and now know what to look for if there's a next time.

 

[Grub54891]

Glad you found it. I’ve installed led lights on two of my trailers. Also ran the grounds completely to the lights. No issues three years later.

 

[abajus]

Glad you found it. I’ve installed led lights on two of my trailers. Also ran the grounds completely to the lights. No issues three years later.

Definitely going to ground each light individually too

 

[wooky30014]

When I brought my "new" boat home all of the lights worked but as I was going through checking everything (and I mean everything) I found a right side tail on the left side with its drain on top, other lights weren't submersible so a complete rewire with submersible LEDs and the trailer ground moved from the trailer frame into the harness white wire. Each light assembly now has its own power and ground soldered and sealed (liquid electric tape over shrink tubes) into the main harness with a second taillight and ground routed down the right side of the trailer

 

[poconojoe]

Theres a pretty good sale on an LED kit right now. Rather than risking the same issue somewhere else after putting the time into fixing this, I'm gonna redo the whole thing. Thanks so much for your help, I've learned a lot and now know what to look for if there's a next time.

I would buy an LED kit that includes all new wires.
If your existing wires are running through the frame, use the old wires as a drag to pull in the new ones. Loop and twist or braid the stripped end of the new wires to the stripped end of the old ones. Secure with electrical tape. Keep it as tapered, tight and small as possible. Have someone gently pull as you feed the other end.

Run a ground to each fixture. Don't just screw the ground to the trailer frame.

 

[wooky30014]

I would buy an LED kit that includes all new wires.

Run a ground to each fixture. Don't just screw the ground to the trailer frame.

Agreed, a kit with the basics and either get another spool of the wire or get more white and brown wire to run a second ground and tail down the right side. Splice them together at the split of point on the trailer. And running a ground to each light is similar to running a separate hot and ground to speakers, they work better that way and it a fault develops later is easier to track down