Trailer lights fine until headlights turned on

New Hopkins converter box and same problem. Trailer ights working fine until I turn the headlights. I guess I can't have running lights and brake lights.

 

Welcome to the Forum!

Sounds to me without really knowing the whole story .

Your out of the Box converter does not work !! The trailer light harness is FUBAR or something is wired wrong.

Maybe explain what your problem is and how you reached this point??

 

Thanks.
I think this is the 4th one for this truck. It came with a Reese converter when I bought it new in 2004 which I replaced with the same 2x. Figured I would try a different one this time. The one this replaced lit all three lights on the tester at once. Put the Hopkins one in and couldn't find where I put the tester so I hooked it up to the trailer and everything worked. At least I thought it did. Guess I will dig in to it.

 

Time to upgrade to a multimeter they are so more useful being able to have real numbers instead of just a light.

Good Luck!

 

it may sound stupid but double check the connections (signal, power, ground) as there could be something amiss

also what type did you get, the plug-in or the "tap-in" variety?

 

What lights aren’t working? I had an issue a while back and everything worked but the blinkers were dim traced it back to the trucks tail light connectors being high resistance and needed some tlc. Cleaned the contacts and put some dielectric grease on them and all the lights worked and trailer harness box didn’t smoke like other ones.

 

The brake/turn signals don't work when the headlights are on. Tried another controller and the test plug shows faint flickering with the headlights on. Connections look good. Used dielectric grease the last two controllers.

 

How is your trailer ground? Alot of trailers ground through the hitch instead of the plug.
Try taking a jumper cable and puting one end on a good ground on the truck and the other end on a good ground point on the trailer and see if they work.

 

I'll try everything at this point. Trying the quick fixes first. Too hot here and I am running out of time before our wagon train heads to our new home.

 

From etrailer questions about Hopkins converter


Hi, I installed Hopkins 43315 four flat wire harness on my 1999 Tacoma and Im using 48655 four flat tester to test the system. With my headlights off, the tester shows the brake lights work and the turn signals work. When I turn on my headlights, only the tail lights work, the brake lights and turn signals stop working. The harness is cleanly and tightly grounded to the frame. Any ideas how to fix this? Thank you

asked by: Hanna

Expert Reply:

What you're describing is a text book ground problem. The ground connection isn't strong enough to handle the load with the running lights on but will handle it when it's just the brake or turn signals. But you said your ground is good.

In this case make sure the pins of the Hopkins # HM43315 are clean and corrosion free. Also check the tester, especially the ground. I'd also check the connector with a trailer instead of just a tester, or check the tester on another vehicle's 4-way. My guess is the tester isn't getting a strong enough ground connection.

https://www.etrailer.com/question-318964.html

 

Thanks for the response.
I tried the test plug on my other truck and it worked fine. Ran a wire from the neg terminal on the battery back to the trailer plug and it still does the same thing.

 

Did you try grounding it to the frame of the trailer?

 

I will reiterate my previous statement, check the connections at the tail lights (if you have the plug in variety) for any corrosion, frayed wires, cut wires, or loose wires.

just because it's new does not mean it's without a possible issue. I've replaced 4 controllers in my 18 years due to them failing and the wires themselves getting corrosion internally

 

I hooked up the trailer and tested everything. The lights work properly. I don't know why the test plug would cause me to go through all this when the problem was the controller from 2 years ago that just went bad. Feel like a dumbass for not double checking with the trailer connected. I checked the new controller with the trailer connected after I installed it and everything worked then.

 

The thing is wiring and plugs and sockets can all be corroded that your naked eyes can not see.

Meter probes sometimes push through the corrosion and appear to work fine.

Given the option I will go with a 7 pin plug and add a separate turn signal light and do away with the evil converter boxes.

 

myself included.

only downside is if you need/want to tow something that is not "your" trailer that has the matching wiring configuration. you would still need the converter for that

 

Ha Ha I thought of that my work around was I built a Custom Light bar that Has a long enough cable to hang on 24' trailer. it works great.

I got tired of Towing Welders in the Wee Hours with not having lights.

If I used it more often I would Go Wireless.