Troubleshooting Wiring Issue On Harbor Freight Trailer
Question:
I have a brand new truck, 2016 ram, and I bought the infamous harbor freight handy man special red trailer non folding model. I just installed a brand new LED light kit because the kit that came with the trailer had bad ground wiring from sitting outside in the weather/sun/corrosion etc... I removed ALL paint from ANY connection point where metal would be touching metal on the side markers, rear lights and grounds. I also removed paint on 2 locations where the tongue V-frame connects to the trailer frame to ensure the ground gets from the rear lights to the front where the ground is drilled into the tongue V-frame. I used di-electric grease at all metal to metal connection points, inside splices, etc... and then covered all connection points with car underbody coating to prevent rust hopefully after the wiring was connected up. I cant think of anything I didnt do to make this work. Im using a 3 foot extender to go from the truck to the light kit wiring harness and it shoots good with my multi meter end-to-end in each wire and each wire-to-ground wire Now to the point. I have no running lights OR side markers. Im thinking about selling this trailer, learning my lesson and spending 4 times as much for a trailer that is put together already with a correctly wired light kit. This trailer is renowned for issues like this......
asked by: Chris W
Expert Reply:
It does sound like you have done the ground wiring well. I recommend putting a circuit tester like # PTW2993 on multiple spots as you test wiring from the truck to the trailer lights. Starting at the truck with the trailer disconnected, test each function of your 4-way. If all checks out, add the extension and check each function. If that checks out, then test right behind the trailer wiring connection to that extension. If everything works at this point, you have 100 isolated the issue to the trailer.
To confirm a good ground, you can run a wire from your battery to your trailer ground. If everything then works you know the ground on the trailer is the issue. If that isn't the issue, then we've ruled out the ground and you will need to find the short in your wiring. For each function on your trailer, test in 5 foot increments because you need to isolate where there is a short and replace that section of wiring. Note that LED are polarized, so if you have the power and ground switched they will not work.
If it is an aluminum frame, try grounding to the axle. If the lights ground through mounting hardware, I recommend running jump wires to a main ground.
If troubleshooting fails, I recommend using the 4-Way Wishbone Trailer Wiring Harness with 42" Ground Wire - 40' Long # A40W42B and simply starting over. I've attached a wiring diagram to assist.

Products Referenced in This Question
4-Way Wishbone Trailer Wiring Harness with 42" Ground Wire - 40' Long
- Trailer Wiring
- Trailer Connectors
- Trailer End Connector
- 31 Feet and Longer
- Plug and Lead
- 4 Flat
- Optronics
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Carl K.
8/8/2020
i have a 2019 ram it has separate blinker from tail light led kit said in needs aditional hardware would like to know what is needed