Why Dont Trailer Lights Work

Question:

I wired up my boat trailer with new harness and lights the lights only have 2 wires yellow/brown green/brown same as the harness every thing is wired right but my lights dont work at all i have nothing.. does the trailer hitch need to be hooked up to the pickup ? Please tell me whats going on im getting irritated.

asked by: Daniel

Expert Reply:

I was unable to find your order number in our system to determine which lights and harness you purchased from us, and you didn't mention what you bought from our site so the best I can offer is general troubleshooting, though I think it'll be a good place to start. And though you mentioned everything is wired correctly, that's possible but I'd recommend staying open to the possibility there was a small error somewhere along the line, which would hamper the whole process.

I am going to assume that you simply re-wired your boat trailer, but in the interest of being thorough, you will want to also be sure the signals are getting through from your tow vehicle. In order to determine the specific problem you will need to purchase a circuit tester if you do not have one - the Cordless Circuit Tester # PTW2979 would be my strong recommendation - and test the connector on your vehicle after disconnecting it from your trailer.

Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring. If the signals going to your harness are okay, you'll need to test the signals coming out of the harness. Additionally, check your vehicle connector for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you are going to need to either replace the plug or clean the corrosion.

You'll also need to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion as this could be the cause of the problem. A faulty ground wire is the bane of many trailer wiring issues so I recommend being very thorough in this regard. You are also going to want to check the wires for any type of nicks or damage that could be hampering the signal getting through, as well as any type of splices. Finally, be sure you have not overloaded your harness with amperage.

I also recommend using Dielectric Grease for Electrical Connectors # 11755 to help prevent any type of corrosion in your connector; using it will increase your trailer and vehicle connector's durability and extend their lifespan.

I have added links to a pair of help articles on trailer wiring, including a troubleshooting guide which I highly recommend taking a look at.