Trailer Wiring - I am stumped

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DavesNotHereMan

DavesNotHereMan

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Guys:
I hope someone has an idea, cuz I am outta them. My running lights don't work.

Coming out of a 7 slot thru an adapter to a 4 flat. The wires were frayed on the trailer, insulation worn off and blew the fuse in the Explorer (tow vehicle) for the running lights. Fuse replaced. A-OK.

Cut the wires, wired in a brand new 4 flat pigtail and used butt joint heat shrink connectors ( they are great). Hooked everything up, including new Ground line. Checked continuity on each line with VOM (old analog Radio Shack - still works). Everything checked out OK, including Ground continuity.

Plug in the connector. Left Turn Signal (yellow)- Perfect. Right Signal (green). - Perfect. Running lights - (brown-green and brown-yellow) - Nothing. WTF???!!! BTW: Running lights and turn signals use a common ground out of the light socket.

Ok. VOM goes to the DC voltage scale. Test the voltage out of the vehicle 4 flat adapter. 12V on all three lines. I expected the turn signals since they worked, but didn't expect the running lights voltage to show up. Pulled the light off the trailer and wired up a jumper to make sure the light worked. Yup, perfect. Went back to that taillight socket and I only get 5v???!!!

So I cut out 1 of the butt joints and I still only get 5v.

So, somewhere between the vehicle and the brand new pigtail that I wired in, I am losing voltage. How is that possible?

If no one has any ideas, my next step will be to cut out the butt joint connectors I used and use a jumper wire directly to the 2 brown lines (running lights) already in the trailer, bypassing the new pigtail to make sure the lights do in fact work and I don't have some other issue.

Thanks, in advance, guys, Any ideas?


-Dave
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Is your flat 4 spliced into the factory wiring? Is the wiring on the trailer side grounded? Meaning is the white wire on the trailer side grounded? I never rely on the ball to make the ground.

Hopkins makes really nice plug and play kits for most vehicles. They plug inline to the tail lights. The go all the way back to the 94 explorer. Wire taps, scotch locks and splices are a thing of the past for me. As a matter of fact I have one from a 96 Explorer. Brand new, installed and NEVER used except to test the trailer light. We wire every vehicle JUST IN CASE. Parents sold the exploder and I took the OEM hitch I put on it and the wiring kit I installed.

I actually had a 7 way RV receptacle take a dump on me so I wouldn't rule that out. I used to run 7 to 4 adapter out of it like you and all of a sudden I lost passenger side tail light. Trouble shot it back to the 7 way.


http://www.hopkinstowingsolutions.c...ring-harnesses/?year=1997&make=FORD&model=462
 
Wow. Quick response, thanx Racer.

The 2005 Explorer has the factory towing package. It is Factory Wired to the 7 way. I had a previous problem with the 7 way to 4 flat so I took it apart and found a loose - as in completely free wire. I took care of that.

I am getting the full voltage out of the 7 way to 4 way adapter. That was my source for the jumper wire directly to the light, which worked just fine. So I eliminated that as a problem. But.., to your point, I used the vehicle ground for that jumper test, not the trailer ground.

Certainly worth a recheck before I cut out the new pigtail.

Yes, new ground wire in the trailer side. Since it is a common ground between the turn signals and running lights, and the turn signals work fine, not really sure how there could be a problem with that ground. I did a continuity check from the light socket (there is a plug in socket on the light) on the ground wire as well and it checked OK. Another good idea to recheck. I will bypass that ground and go straight to the vehicle ground (white) before I cut out that pigtail. If the lights work, then somehow the ground is fine for turn signals, but not running lamps.

I just can't seem to find why the voltage is wrong.


-Dave
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A loose or floating ground can be a killer. Is the ground on the tail light a separate wire or is it a mounting stud that uses a star washer to "complete" the ground? Are these incandescent bulbs?
 
When the turn signals are on are they bright and solid? Or does the opposite tail light dimly blink?
 
No formal ground white wire connected to the trailer frame will get you chasing your tail every time. Also dangerous b/c your trailer lights might not work that one time when you need them most.
 
The connectors to the tail lights are a plastic press on device with 3 pins. 1 for Running (brown/yellow stripe - Left, brown/green stripe - Right), 1 for Turn/Brake (yellow-left, green-right) 1 for common ground (white). The lights are either LED, or throwaway, since it is sealed and I cannot get to the bulbs.

The turn signals are strong and bright with no bleed. That's why I concluded the new ground was OK. It's the same ground wire from the light to the trailer frame for both running and turn lights. It is attached to the frame at the factory with what looks like a rivet, but it is about 3/4 inch longer than a flush rivet. I am going to bypass the entire trailer ground circuit with a jumper from the light to the vehicle ground (white), though, just to verify.

Racer, you got me thinking about that 7 way. I am going back to the beginning and make sure I get multiple readings at 12 volts. Just maybe I am getting sporadic voltage out of the 7 way or the adapter or even the vehicle wiring harness. If you had one crap out - well anything can happen, I guess. I am going to test that 7 way today. I guess another test I can do is bypass the entire vehicle harness and use my SeaDoo battery (it's an AGM and not installed back into the ski, yet) as a voltage source.

I know these electrical things are a PITA and this one makes me want to tear out whatever hair I have left.

I will test some more today and post back later.

Thanks,


-Dave
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So today I check it and there is 0 voltage on the running light pin. Blew another fuse.

The factory wiring has a 20A mini-blade fuse just for the trailer running lights in the electrical box under the hood. This is the second blown fuse.

Replace the fuse and I get 12+ volts at the pin.

Now the question is .. Why are the fuses blowing? I am going to drive around without anything connected and see if the fuse blows. If so, that would seem to point to a short somewhere in the factory wiring harness. That would be bad as I have no way to trace it.


-Dave
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Dave,

Are the tail lights new or were these in use before this problem?

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Ok. Drove around running errands all afternoon. Checked the output when I got back. Full Pull. 12+ volts solid on all pins.

This weekend, I will pull out one of my other trailers and see if everything is OK. If so, I must have a short to ground somewhere on the trailer.


-Dave
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I had an issue a few years back where the trailer wire harness was rubbing the stud of a bolt. I'd hit a bump and blow the fuse. I bought a new trailer wire harness, installed it, problem solved.


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Last edited by a moderator:
Ya know, Coastie, that is beginning to sound mighty fine. I have certainly spent more time on this then a new trailer harness install would take. I just wonder if one of the lights itself is shorted out. I could disconnect them all and check them independently, I guess.


-Dave
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DavesNotHereMan said:
Ya know, Coastie, that is beginning to sound mighty fine. I have certainly spent more time on this then a new trailer harness install would take. I just wonder if one of the lights itself is shorted out. I could disconnect them all and check them independently, I guess.


-Dave
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Click to expand...

Super cheap,, I ordered new LED lights and a harness from eBay. In fact,, I'll find my post where I added the lights to show you how I soldered instead of crimped them. And I LOVE the LED lights. So much better... Never unplug them and they are MUCH brighter..
 
Yea, they are nice! I am really leaning to just replacing the harness as you suggested. How did you do your marker lights? Same way? Cut, solder, heat shrink? The trailer in question uses those clamp type connectors where you don't strip the wire but lay it in the clamp and squeeze this blade thru both wires. And that gets submerged.


-Dave
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This are scotch locks Dave. I'll use them for a temporary fix. The best way is solder and shrink tubing. Harder, but you never have to mess with connections. Just hook 'n book!

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Ah. Scotch locks. Thanks, did not know what they were called. I hate 'em!

The butt connectors I used have something in them that oozes out when you heat shrink them so they are waterproof. I was fairly impressed. I got them at HF, which is good for some things, not so much for others.


-Dave
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DavesNotHereMan said:
. How did you do your marker lights? Same way? Cut, solder, heat shrink?
-Dave
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Click to expand...
Yep, I did them the same way. As a polite reminder,,, make sure you slide the heat shrink onto the wire BEFORE you solder them,, Though I didn't make that mistake this time, I have done it before..

Doing the solder and heat shrink thing is really the best thing to do. Any, including butt-connectors, joints that hit the water will fail. It is a question of time. Also, the connection to the wires can be poor right from the beginning and the lights will have less than expected performance. Dim under a load and what not..
 
Good stuff!

That heat shrink doesn't shrink when it is sliced up to fit over wires. Ask me how I know!! lol!!

We used to put silicone caulk in a straw and slide it over the joint in the olden days. It actually worked great if you did it right. The big milkshake straws worked the best.


-Dave
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I could see the silicone in a straw trick working... Even my old regular taillights were "submersible" But every now and then it would pop a bulb. Between the harness and the LED lights I never unplug the harness anymore..
 
Check behind the lights, I've had a lot of pinched wires behind the lights when the rigger mounted the light fixture on the trailer the wire was pinched when the mounting bolts were tightened.

LED lights are nice, I don't need to change the turn flasher to heavy duty type anymore and lets me preserve the regular light duty flasher with no flash feature when a turn bulb on the car is out.
 
We are pulling the boat for out drive service tomorrow. I will plug in the flat. If I blow that fuse, then I know there is a short in the trailer brown wires. I am going to take a cursory look as you suggest to see if something is obvious, but if not, I am going to replace the wiring harness.


-Dave
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Dave, what are running lights? I just made a new thread, need help understanding basic terms before I replace my broken lights. thanks
 
Easiest thing to do is to go to etrailer dot com. There are great descriptions there of complete trailer wiring.

The running lights are the "normal" brightness when your headlights and tail lights are on. Then there is a brighter light when you turn on the turn signal or press on the brakes. I always test mine by plugging in the connector, turn on the headlights (lights up the running lights) and flip on the hazard lights. This will show you if every light on your trailer is working correctly.

Most trailers, like PWC trailers, have 4 wires and a ground. 2 of the wires are common, so they are wired together in the "flat" shaped connector which has 4 contact pins or posts. The trailer has 3 male and 1 female pins on a 4 pin "flat"

If there are electric trailer brakes or batteries, there are more wires.

My tow vehicle has a 7 wire connector, which has an adapter that allows the "flat" 4 wire connector to plug into it.



-Dave
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