fuses blowing with new trailer harness...

[jayson44]

I bought an old military trailer for Father's Day and the wiring on the lights was all old, cracked, and messy. so I tore it all out and bought new lights and wiring. I finally got around to wiring it up today. I thought it would be pretty straight forward...got the lights in place and the two wires coming from them said to go to either tail lights or turn signals, so I wired them accordingly. ran the wires up to the front and joined them with the end of the harness (4 pin flat). plugged it all in to test and that's where the trouble began.

with the headlights turned on, the trailer lights lit up just fine. when i went to turn the blinkers on, bam, fuse went. I replace the fuse and tried again. this time, the fuse held, but no blinking on the trailer. then I tried the brake lights. bam, fuse out. replaced the fuse and tried again, same results. I thought maybe the wiring was wrong somewhere. my test light indicates that the Jeep side harness is correct, and I even hooked the test light ground to the ground on the trailer (which I thought might be sketchy) and it ran the test light just fine. I even unhooked all the wiring from the trailer to try to test from the wire side, but again, any time the Jeep is plugged into the trailer side and the brakes are applied, the fuse blows.

any suggestions? I'm not the greatest with wiring, so I'm not sure what to test. Jeep side harness was installed by me, spliced into the main wiring harness per past experiences on other Jeeps (a TJ and a CJ). just not sure what's making the fuse blow...

J.

[BLOODBANE]

Bad ground on the trailer? I would check them all.

[Hypoid]

Yup, short to ground in the trailer harness. Are the trailer lights LEDs?

[jayson44]

lights are not LED...just the cheap 4" rounds w/bulbs inside:

http://i298.photobucket.com/albums/mm251/jandkcarlson4/jeep%20stuff/6E436F71-3CA7-4F7B-86AC-7E1EFFC84076_zpsutmriuvi.jpg (http://s298.photobucket.com/user/jandkcarlson4/media/jeep%20stuff/6E436F71-3CA7-4F7B-86AC-7E1EFFC84076_zpsutmriuvi.jpg.html)


I do think the ground to the trailer isn't the best, but it's not the worst either. maybe I need to try to sand down the spot to make sure there's no paint underneath. here's the ground:

http://i298.photobucket.com/albums/mm251/jandkcarlson4/jeep%20stuff/E80BD78C-A9E5-4D2A-8F3F-0E39A825A59E_zpssltmruwi.jpg (http://s298.photobucket.com/user/jandkcarlson4/media/jeep%20stuff/E80BD78C-A9E5-4D2A-8F3F-0E39A825A59E_zpssltmruwi.jpg.html)

J.

[xaza]

A bad ground will make them not work but won't blow fuses. If you have a multimeter test resistance between trailer ground and each other wire (with Jeep not connected) There should be some resistance on all wires. If you find one with around 1 or less ohms that is your short and then you trace the wire by hand to look for bad section of wire. Sometimes it is easier to just run new wire than to chase it down.

[Hypoid]

lights are not LED...just the cheap 4" rounds w/bulbs insideYou have the wires crossed up somewhere. The wire for the turn/stop filament is shorted directly to ground.

I have more questions now, there is a lot I don't know about your vehicle:
Are the stop/turn circuits protected by the same fuse?
What amp ratings are these fuses?
Are the stop and turn on the same circuit, no yellow lens on the taillight?

[jayson44]

the wiring is all brand new, I just ran it yesterday. as for the Jeep, it has LED tail lights, but I spliced the harness into the main one before the tail lights. would that make a difference?

J.

[jayson44]

so yeah, no yellow lens on the Jeep, and the fuses are on different circuits. 10amp for the blinkers, 20 for the brakes.

J.

[Hypoid]

I'll have to go look up a wiring diagram, but I still think you have a short to ground.

[xaza]

Not sure if you had a diagram
http://www.johnsontrailerco.com/wiring_diagrams.php

[jayson44]

ok, so with everything unhooked from the trailer side, (I cut all the wires off from the lights, so the trailer harness is just wires hanging there...) if I plug the Jeep into it, the breaks still blow the fuse. the only thing still hooked up to anything is the trailer-side ground wire. does that make any sense?

J.

[xaza]

sounds like your short might be in the plug, but if a wire got nicked while pulling it through it could be shorting out there. You are going to go through a lot of fuses if you try to trace this without a meter. You can try and cut all the wires just after the plug (make sure to pull them apart to make sure they aren't shorted) and try again, if it blows then I would say it is the plug. With the wires all disconnected at the lights end it should be real easy to find using ohms or continuity. Would be willing to look at it for you but it is a long drive to me without working lights and I am on call and not able to get to you. Another possible idea is to get a set of magnetic towing lights and try them. Could possibly get it mobile to be able to get some help. You could possibly have wires wrong at the jeep but it doesn't short until the trailer is connected. Re check all those connections with a test light. With hazards on you should have power to green and yellow. Headlights should power brown and you should never see power on the white wire. I would recommend connecting the white wire to the body or frame with a self tapping screw. If you have power on the white wire it won't short until the trailer is connected to complete the loop.

[jayson44]

ok, so if the only wire hooked up on the trailer is the ground wire, and I plug in the Jeep, should fuses blow? it seems like the brakes blow as soon as the plugs touch (wife holding the brake pedal down).

J.

[xaza]

If the only wire on trailer hooked up is the ground and you have the vehicle wired with power to that wire yes it will blow the fuse when trailer is hooked up. The trailer is able to be grounded back to the vehicle somewhat through the hitch. Can you show us some pictures of where you spliced into tail light?

[jayson44]

I don't have pics of where I spliced into the main wiring harness, but I followed the online instructions as far as colors go, and tested the plug when I was finished. seems to be working just fine.

J.

[xaza]

How did you test the plug? What do you have for testing tools? Voltmeter, multimeter, test light?

[jayson44]

I tested with a test light. I do have a multimeter that I could use, but I don't really know how to use it. :) I know it measures things, but I'm not sure how much output each thing should give...electrical is NOT my forte.

J.

[xaza]

Since you have the right tools I can most likely talk you through testing it over the phone. My number is on rescue list.

[xaza]

What happened with this, you get it fixed?

[jayson44]

I've been too busy to take a look as of yet. hopefully this next weekend I'll have a chance.

J.

[jayson44]

ok, so I finally got around to having a little time to check this out. I went back to the Jeep side and started testing the wires. seems as though all of them have power even when the Jeep is off. no bueno, right?

I grounded my test light on the bumper and the light comes on at every part of the trailer plug. even the ground. so I cut the white ground wire from where I had tied it into the Jeep and tried it again grounding the wire to the body. it still has power. does that mean that somewhere the body is getting power from something constantly?

J.

[xaza]

Sounds like you have a combination off issues. Not likely you have a short to ground somewhere else unless other fuses have been blowing. Remove all wires for trailer from vehicle and and test resistance or continuity between each plug on trailer harness. You should have infinite resistance or no continuity between each one. If there is continuity then you have a bad plug and it needs to be replaced. Once plug is confirmed connect white wire to chassis ground and start to connect the other wires one at a time, testing along the way. Confirm wire with test light then connect to trailer harness, then check trailer plug.

[jayson44]

ok, are you saying to test the plug with the meter or the test light? sorry, I'm such a newb with electrical stuff.

should the plug on the Jeep light up the test light even when the Jeep is off and no lights are being "activated"?

J.

[xaza]

You will want to test the plug with a meter. It should not be lighting up constantly. It should never light up on white wire. Brown should have power when tail lights are on only. Yellow and green will flash with turn signals or light solid for brakes. Once everything is disconnected from vehicle using meter on ohm scale check between each of the ends of the plug. It should read as open, OL or 0. If resistance is found between any 2 parts of plug then plug needs replaced.

[jayson44]

k, thanks. I'll try to check that out this week some time.

J.

[88Toy]

It sounds like you're using this plug on the vehicle side
http://pics.montypics.com/88ectoy/2014-09-05/1409944031_sam_0552.jpg

Typically, the exposed pin is the ground. The socket next to it is the running lights. The socket next to that one is the left turn/brake light and, finally, the end socket is for the right turn/brake light.

Take your test light, grounded to the truck chassis and touch the ground pin. There should be no light in any switch or turn signal configuration. If there is, you've got it connected to a hot wire. Check the other sockets accordingly using the ground pin on the plug after verifying. Once you establish this truck plug is correct, you can move on to the trailer side.

Make sure the trailer ground is good between the plug and all light fixtures. I normally run a ground wire for this, not relying on grounding through the trailer chassis but either way is fine, just make sure the ground wires attach to clean, bare steel. With that done, check the new harness for cuts or tears in the insulation that could result in a short with power applied. With all that good, use your test light for power at the light fixtures in all light/turn switch configurations. You should have it if no wires are broken.

[jayson44]

that's correct, that plug is on the Jeep. however, when I ground my test light to the frame and touch the ground pin on the plug, it lights up. so I cut the white wire and tested again. no light. touched that white wire to the Jeep body (to establish a ground) and touched the pin again...light on.

so when the white wire is grounded to the Jeep's body, the pin on the plug still produces a light.

J.

[xaza]

Give me a call, this is not adding up right.

[88Toy]

What about the other power sockets on the truck plug? Does the test light indicate properly with the test light grounded to the chassis(running, brakes, turn)?

[jayson44]

somehow, I crossed the left and right blinkers because when I test, they're opposite. but I SWEAR I followed the online wire-color-diagram correct for my Jeep. but otherwise I get some funky readings regarding the brown wire and they all sort of light up no matter what's going on.

I'm at work at the moment, but tomorrow afternoon I may have a chance to check these out. or sunday afternoon. and Cliff, I'll try to give you a call when I get to work on it.

thanks for all the help, guys.

J.

[jayson44]

I have a sneaking suspicion that whoever the PO had wire the lights on the Jeep did something really funky. for instance, the front CJ-style blinkers only blink, they won't turn on with the parking lights. only the side markers show when parking lights are on. and it appears that they just cut the wire for those front markers. the passenger LED taillight has a ground issue as well, making it turn off every once in a while.

and I won't even start on the "upgraded" alternator and the janky wiring that is involved with that!

J.

[88Toy]

It's funny what some folks call 'improvements'! Keep us posted.

[88Toy]

Ever get this figured out?

[jayson44]

no, I've not had the time yet. MTB race last weekend and my wife did a duathalon yesterday, so we've been super busy. maybe this next weekend.

another thought: my passenger taillight always has issues with the ground wire. if it's not positioned just perfectly, the light won't work (common issue with the LED taillights). I've not gone in and fixed it yet, but could that be giving some issues with the trailer harness at all?

J.

[Jim]

If you'd wish to stop up to my place we should be able to get it sorted in one shot (an afternoon??).

With the jeep off (no tail or brake lamps on) the jeep side connector should have zero volts coming out of it. If you have +12vDC on any pin (between pins or pin to chassis ground) something's wrong on the jeep side.

LED's, when direct replacement for incandescent bulb, should not have any effect upon vehicle wiring. (but I could be wrong / willing to learn the errors of my ways).