I am running new lights on my little trailer as I need it Tues night to move . Well I wired them up and nothing happened . I have power at plug and at wire end at light . I ground my test light on the jack in the front and touch it anywhere on the trailer and it lights up . What is going on here . I need this fixed tonight cause I am moving Tuesday .
I know the truck end works , it worked on my boat last Saturday .
Thanks

 

From what you're saying, it sounds like the lights SHOULD light. But, bear with me, since they're not.

I assume you have a probe on your test light that you can insert into the bulb socket and touch the positive pin? If not, get an inexpensive VOM from someplace like Harbor Freight that gives you this capability. If you probe the positive bulb feed in the light socket and the ground feed, do you show voltage?

If not, the sockets are not connected properly (since you say you have voltage at the wire end. It sounds like one or the other of the connectors from the socket is not wired properly to it's corresponding input. I know you have a positive wire to the socket. Is the negative socket tap connected to a wire or is it connected to the trailer frame?

And, I'm bothered by this: "I ground my test light on the jack in the front and touch it anywhere on the trailer and it lights up ." Something's not right. You GROUND your test light to the jack (in the plug?) and touch the trailer frame with the other lead? Are you saying you ground your test light on the trailer frame and then touch the +12V tap in the plug? (You shouldn't get anything if BOTH leads are grounded).

Sorry for the third degree - I'm just trying to understand what's really going on.

- Jack

 

I will test the socket in the morning .
I grounded the test light on the trailer lift jack and touched the probe to the trailer frame and it lights up . Seems to me something is wrong there , could it be a stripped wire touching frame causing that ? Getting frustrated by this , I have wired many mnay trailers in my life and never had I had a problem like this . I bought this trailer 3 years ago but never used it for anything besides behind atv around the farm . I sold my big trailer and now need this one on the road .

It is an OPTRONICS light kit I she bought at the auto parts store , the wires just stick in the back of the lights and are pinched in place by the socket contacts it looks like .

Thanks for the advice .

 

The lights ground by the light casing bolts to the frame . I usually still run a ground wire to the frame anyways .

 

We're running out of time, aren't we?

Your idea of running a ground wire to the frame is good insurance.

We need to talk about the trailer towing plug at the back of your truck. What are you using? Is it a 7-pin plug or is it a 4-pin plug? SSCULLY, just recently posted a 7-pin diagram here: https://www.f150online.com/forums/3652476-post14.html

If it's the 7-pin plug, just probe with your test light between GND (at 7:00 o'clock and the pin at 11:00 o'clock (running lights), the one at 9:00 o'clock (Left turn/stop light) and the one at 3:00 o'clock (Right hand turn/stop light). You should see voltage or your test light should light up when any of these systems are active.

If the 4-pin plug, the "exposed" pin is GND, the other three are Stop/Turn and Running lights. Again, you should have voltage between GND and any of these others with the appropriate system activated.

If you don't, the problem is in your truck somewhere.

If the plug checks out, the problem is in your trailer. With the trailer plugged into the truck socket, do you get voltage between a light center tap and the frame with the appropriate circuit activated? If not, the light sockets are probably not connected properly to the trailer wiring. My guess is, that's the problem, but you need to rule out the other possibility.

Remember, for the turn signals to flash at the trailer, the truck's turn signals need to be flashing. For the running lights to be on, your truck's lights have to be on too.

I'm sorry I'm not more help than this, but this is really all there is to it. You either have voltage at the truck's trailer plug or you don't. It's more complicated to find the fault if there is no voltage there. If the plug has voltage, the problem is in the trailer wiring, and that is pretty simple.

Good luck on this!

- Jack

 

4 pin plug . The truck works fine on my boat .

 

Dumb question of the day for me ( actually I usually have 5 or so, but I am hopeful today is the day ), is this one of those trailers with the rubber mounted tongue to stop it from jerking around ?

I thought I saw that on a trailer somewhere, usually it is rubber mounted axles in place of springs.

If the tongue jack is still on the truck side of the grounding, and you bridge it from there to the remainder of the trailer frame and it works, I would say there is an insulator in the path somehow ???

Try a quick additional ground wire from where the 4 pin is at on the front of the trailer, and run it back farther on the frame, and see if it does the trick.

This is one of the reasons I run 14 AWG flat 4 all the way back on the trailer in a Y ( down each side of the trailer ) and solder T-tap the wire from the lights to the backbone flat 4 wire on the trailer.
With the 7 pin, I usually add in a 12/3 SJOOW cord down the length of the trailer as well. E-Brakes are right up front, so that gets 10 AWG, and a 10 AWG ground from the 7 pin.

 

Great thought SSCULLY! Even if there isn't a rubber insulator in the setup, there could easily be a poor ground path. I once had to install a ground strap between the bed of a pickup and the cab to make the rear lights work. Over time, corrosion or dirt had made the overall truck frame a very poor ground path.

Since your boat's lights work, coonhound, it's clear to me that the electrical fault is in the trailer. And, since you installed new lights on it, I'd concentrate my troubleshooting on the connections, assuming you have continuity between the trailer frame and the truck frame.

- Jack

 

It was a poor ground on the trailer frame , I could not get the frame to ground anywhere , so what I done was Just run the ground from the plug alway to lights and they work now . The tongue would ground if on the ball hitch but that was it , just the tongue and nowhere else .
Thanks for the help

 

Great! Glad you found the problem in spite of all this somewhat confusing advice!

The only reason I feel I can talk intelligently about DC electrical circuits is that they're simple! You basically just have to have a complete path from source (the battery) back to destination (the battery). If that path is broken anywhere, the device doesn't work. (There are a few small wrinkles like excessive resistance and short circuits, but they don't crop up much).

- Jack

 

Thanks again for the advice . It will come handy in the future for sure