# new trailer lights do not work



## randyo3629 (Dec 19, 2021)

2006 polar craft trailer.
picked up the boat..the only lights that worked were the side markers on the tongue.
.
replaced the trailer harness and the rear lights with LEDs
plugged into the truck...same tongue lights were only ones on.
connected truck to another boat trailer.....all trailer lights work.

cleaned all three ground points.. shiny and tight
reconnected to truck...same result.

here's the kicker...

connected light harness straight to battery.....all lights work, with the exception being the tail lights.
bypassed all the side markers .....same result still no taillights, when connected to battery....or truck

WTH!!

i've replaced harnesses and lights before and never had this issue.
hope someone can enlighten me.
thanks


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## maintenanceguy (Dec 19, 2021)

I don't know what the problem is but I would use a volt meter to check every wire coming out of the truck's trailer connector. Check the voltage to ground with the various lights on and off (tail, blinker, etc.). At least that eliminates (or proves) the truck as the problem.

All of the problems I have had with trailer brakes have been ground issues. I now just run a ground wire all the way to the tail lights and don't use the trailer frame as the ground.


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## MN Fisher (Dec 19, 2021)

maintenanceguy said:


> All of the problems I have had with trailer brakes have been ground issues. I now just run a ground wire all the way to the tail lights and don't use the trailer frame as the ground.




I still use the frame - but put jumpers in at joining points...like the front-section to rear-section of the current trailer


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## randyo3629 (Dec 19, 2021)

maintenanceguy said:


> I don't know what the problem is but I would use a volt meter to check every wire coming out of the truck's trailer connector. Check the voltage to ground with the various lights on and off (tail, blinker, etc.). At least that eliminates (or proves) the truck as the problem.
> 
> All of the problems I have had with trailer brakes have been ground issues. I now just run a ground wire all the way to the tail lights and don't use the trailer frame as the ground.



i dont believe it is the truck. hooked up to my boat trailer and all the lights work..
just strange that the lights work the same with the new harness as with the old harness,


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## randyo3629 (Dec 19, 2021)

i was thinking.....the marker lights in front of the tongue pivot work. the marker/tail lights behind the pivot do not work.
possibly losing ground thru the pivot?
may need to run separate grounds to lights?


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## GTS225 (Dec 19, 2021)

Did you read maintenanceguy's post from two hours ago?

YES, run dedicated grounds to all lighting. Don't rely on the trailer frame to complete your lighting circuit(s).

Roger


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## GYPSY400 (Dec 19, 2021)

You have a ground problem. Does the trailer pivot or bolt together behind the front marker lights? You will have to run jumper wires between the pivots/ bolted sections or run ground wires all the way back to the rear lights.

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## Rumblejohn (Dec 20, 2021)

Don't forget that LED's are polarity sensitive. If you have power to the socket, try reversing the wires. If not make sure that there are no broken wires and you have a good ground.


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## randyo3629 (Dec 20, 2021)

GTS225 said:


> Did you read maintenanceguy's post from two hours ago?
> 
> YES, run dedicated grounds to all lighting. Don't rely on the trailer frame to complete your lighting circuit(s).
> 
> Roger



yes i did....makes total sense.
i really think the problem has to do with the tongue pivot.


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## GTS225 (Dec 20, 2021)

randyo3629 said:


> yes i did....makes total sense.
> i really think the problem has to do with the tongue pivot.



Hence the advice from at least two people to run ground wires, rather than rely on the frame for grounding.

Roger


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## GYPSY400 (Dec 21, 2021)

randyo3629 said:


> GTS225 said:
> 
> 
> > Did you read maintenanceguy's post from two hours ago?
> ...


Ahh ok, that makes sense.. run a jumper wire across the pivot, leaving enough slack in the wire that it doesn't pull the wire tight while articulated. 
You can use self tapping screws to secure the wire eyelets, or drill and tap 1/4" bolts. 

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