Trailer light gurus, help!

Wes

Wes

Well-Known Member
Joined
Oct 14, 2007
Location
Ridgeway, SC
Info:
Boat trailer with a 4 pin connector. I have brake lights, turn signals, and the rear running lights. My issue is with the side markers. The previous lights didn’t work so I installed new LEDs for the side markers only. I have 12 volts at each light, but they no workie. To rule out the truck I used an extra battery I had laying around and rigged up connections. Once again everything worked but the side markers. The only thing I haven’t done is removed and cleaned all grounds. A visual inspection doesn’t look like any bad grounds though. They’re all super tight. I’m at a loss. Any help or suggestions are appreciated.
 
Any chance they're wired backwards?

I'd hook the spare battery up right at the light, go from there.
 
shawn said:
Any chance they're wired backwards?

I'd hook the spare battery up right at the light, go from there.
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The brown wire is my running light from the connector. Each light is connected to the brown wire and grounded to the trailer. I thought about your idea as well, I just hate to undo all of my pretty connections.
 
Wes said:
The brown wire is my running light from the connector. Each light is connected to the brown wire and grounded to the trailer. I thought about your idea as well, I just hate to undo all of my pretty connections.
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Agreed. I'm just thinking that maybe the pos and neg sides of the LED are backward (even labeled so). If the LED is known good and has hot and ground, that's the next likely cause. You can check the LEDs with a meter, but you're going to have to cut a wire to do that, too.
 
shawn said:
Agreed. I'm just thinking that maybe the pos and neg sides of the LED are backward (even labeled so). If the LED is known good and has hot and ground, that's the next likely cause. You can check the LEDs with a meter, but you're going to have to cut a wire to do that, too.
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I’ll mess with it tomorrow and report back. The trailer wires are piano wire tight. Whoever wired it from the factory left absolutely no slack. They’re so tight that if I cut them I’ll have to add more wire to reconnect them. It’s ridiculous.
 
Wes said:
I’ll mess with it tomorrow and report back. The trailer wires are piano wire tight. Whoever wired it from the factory left absolutely no slack. They’re so tight that if I cut them I’ll have to add more wire to reconnect them. It’s ridiculous.
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Did you hook the battery up at the trailer plug before? Do the same thing, but put neg on the brown and pos on the white. If that works, you know they're backwards.

How did you confirm that there was power at the light? Probed through the insulation?
 
shawn said:
Did you hook the battery up at the trailer plug before? Do the same thing, but put neg on the brown and pos on the white. If that works, you know they're backwards.

How did you confirm that there was power at the light? Probed through the insulation?
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Yep. I skinned back the running light wire and checked it and the ground with a multimeter. 12.3 volts to be exact. Good idea on swapping the ground and running wire at the connector. I’ll try that tomorrow. Thanks.
 
are we sure the lights are good?
Are these sealed side markers or did you install new bulbs inside a replaceable housing
 
Ron said:
are we sure the lights are good?
Are these sealed side markers or did you install new bulbs inside a replaceable housing
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New sealed led’s. The old incandescent lights didn’t work, swapped them with these led’s and still no luck. It’s possible they’re bad but that would be weird to buy two bad lights off the shelf at the same time. It’s definitely possible with my luck though.
 
Worse case start ohm’n wires and see what isn’t making a connection. Have you every used a power probe or have a fascination with just buying tools Tim Taylor style?
 
Are these the type of lights that ground through the mounting stud or are they a 2 wire light.
 
yager said:
ground at the light ?
They are sopose to have a star washer,
get bogger up at times, wires bush the metal, and make sure it has ground.
Very common problem on boat trailer.
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They each have their own ground. I’ll try cleaning up the trailer under the grounds.
 
Ron said:
Are these the type of lights that ground through the mounting stud or are they a 2 wire light.
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Two wire light. One is spliced to the running light wire. The other is grounded on the stud. The old incandescent lights were a single wire spliced to the running light wire.
 
LEDs have a much lower current draw than incandescent. It's one of the reasons they are so popular in commercial operations. (Lamp life being the other)

One of the consequences of this. The lower current draw makes them more susceptible to weak grounds with less energy in circuit. I've seen intermittent burn and dim run issues if grounds aren't very low resistance. I ended up running an electrical ground on my whole trailer for that reason and using a circuit ground as opposed to a frame ground.

But it doesn't change that your old incandescent weren't burning either.

To me this is one of the back to basics trouble shoots. Re verify everything you've already checked.. make sure you are getting 12v. Verify the new lights direct to a battery etc
 
Ron said:
LEDs have a much lower current draw than incandescent. It's one of the reasons they are so popular in commercial operations. (Lamp life being the other)

One of the consequences of this. The lower current draw makes them more susceptible to weak grounds with less energy in circuit. I've seen intermittent burn and dim run issues if grounds aren't very low resistance. I ended up running an electrical ground on my whole trailer for that reason and using a circuit ground as opposed to a frame ground.

But it doesn't change that your old incandescent weren't burning either.

To me this is one of the back to basics trouble shoots. Re verify everything you've already checked.. make sure you are getting 12v. Verify the new lights direct to a battery etc
Click to expand...
I’m seriously considering just rewiring the whole trailer and make everything LED. It almost seems easier than trying to troubleshoot.
 
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