Trailer Lights shortening out....

[Seadoobuddy]

In my Chevy Trailblazer I keep popping the trailer tail light fuse....10 amp
The Turn signals work.
the brake lights work also.
I've put a trailer test light on it and it doesn't pop when I turn on the truck lights

I have disconnected all the lights from the wiring harness, (both tail, the 3 light center strip set and all 4 side lights).
I've put a meter (set on ohms) at the trailer plug, one lead to each of the 3 "connectors"...tail, LT & RT.
Only the LT has no change in the reading on it.
The other 2, the meter goes from 1 (infinite) to 1.3 up to 6.1 always changing.

Does that mean I have 1-2 bad wires going thru the trailer body.

The fuse only pops when I turn on the truck lights.....so as long as i don't tow at night I'm OK ?!?!?!?!?!

 

[RFoster130]

I had a similar problem. I rewired my entire trailer and installed all new LED lights. I still kept popping the fuse on my old truck, the 2005 avalanche. It seemed intermittent and i couldnt figure out the problem. I suspected the adapter plug. On the truck with the tow package it had the big round 5 or 7 way plug with the 4 flat on the end. When i got the new tahoe with the new adapter exactly the same, the problem went away. So im guessing my problem was something on the plug adapter. I think maybe it was kinda sloppy in the hole, or possibly a bad connection on one of the contacts. Im not sure which plug your trailblazer uses, but if its one of those type, i would swap it out and see what happens.

 

[Seadoobuddy]

It has the 7 way with an adapter to the flat 4 pole plug.
thanks for the idea.
Although I edited my first post to say it pops after I turn on the truck light with the trailer attached. It doesn't pop if the trailer is NOT attached.

 

[RFoster130]

mine didn't pop unless the trailer was attached also. check that adapter good. you can find em on ebay for like 6 bucks.

 

[Seadoobuddy]

Thanks Rich.
I had the adapter on with the tester plugged in and it didn't pop.
How does the trailer being attached affect it differently? ....pulling more power for all the lights? 9 of them.

 

[RFoster130]

who knows...lol. Maybe without pulling a current through it doesnt affect it. It might not be your problem, just a suggestion. I knew all my wiring was good since it was new, i just narrowed it down to that.

 

[racerxxx]

Ok, here's what I think your saying:

Truck only--everything works

Truck with 7 to 4 adapter-- everything works

Truck with 7 to 4 adapter and trailer plugged in-- brake lights and turn signals work

Truck with 7 to 4 adapter and trailer plugged in--turn on running lights--Fuse blows

I also assume when you mean a trailer test light you mean one of those flat 4 jobbies with the LED's on them to check truckside.

If that is the case then somewhere on the brown wire you are touching bare metal. That is the feed for your running lights. Without the running lights your brake an turn signals work, same element on the bulb.

With your meter still set to check continuity go from the brown wire directly to the trailer(anyone of the open browns or right at the plug). If your meter shows resistance then somewhere that brown wire is touching the frame confirming there is a short.

 

[LouDoo]

Tim, go over to Harbor Freight and pick up a new set of LED lights and wiring, for 40 bucks is ain't worth screwing around with the old wiring.

http://www.harborfreight.com/led-trailer-light-kit-95974.html

Lou

 

[Seadoobuddy]

Lou, i just bought one of those for my new/old trailer in florida.
This problem is with my boat trailer. it has 4 side lights, 2 rear light + a center set of 3 lights in a strip on the back of trailer. So i guess i would have to splice a lot.

Racerxxx, your 4 points are right on the money. I/we have tested the brown wire at both tail light connections. There is a reading on both sides of the trailer.

Yes the tester is the flat 4 wire one.

From the front harness plug they are 2 brown wires...one w/green for the passenger side and one w/yellow for the driver side. We thought we found the short but then we couldn't get it to read 1 again. They all have some sort of reading.
Every access hole has a plastic ring around them to prevent wearing off the rubber coating of the wires.

so maybe it's time to rewire the trailer, it is 21 yrs old w/original wiring.

 

[sselzer]

Check your ground.

 

[Seadoobuddy]

Check your ground.

Thanks, but I would have to assume the ground is good since the turn signal and the brake lights work.

 

[RFoster130]

I would rewire it. Harbor freight sells the kit for like 8 bucks. Thats what i used plus all new LED lights off ebay....$75 later it still kept popping the fuse. The $6 adapter was the issue.

 

[bigJake]

Trailer Lights shortening out....

Oh Timmy,
could be the Crisco... try putting them in vegetable oil instead of shortening

and check your compression.

 

[Wenier]

I would check the truck wiring to your trailer plug.

I had a similar issue in my ute where with a trailer hooked up it would blow a fuse when selecting reverse. At first thought it was the trailer but then when a towed a near new car transporter that I knew was good and it happened I knew it was time to look at the utes wiring.

Anyway long story short the person who installed the trailer plug on the ute had used the reverse light wire as an earth, so of course when selecting reverse it would pop the fuse, surprisingly the lights still worked using that wire as an earth. I simply brought a new plug and did a proper job of it with heat shrink solder and all. (they had twisted wires together, taped them and that was it.)

 

[Seadoobuddy]

PROBLEM GONE at least for now

I removed all the lights to inspects the wiring...all seemed good.
The only light that i forgot to test with the meter was the license plate light. So i messed with that today, didn't see anything wrong but I pulled it out a short ways to inspect, then I pulled the back light wiring that it's attached to and recheck it with the meter.....all were good readings at all connections. I reinstalled the light and hooked it to the truck and all worked. Drove to ramp (unplugged the lights) backed up to pick up my boat, reattached the lights and they still worked.
Drove home a whole 3/4 mile trip . emptied the boat and stored all the stuff and will winterize it on Sunday...temps should be in the high 60's maybe lower 70's....dang it...LOL

So I assumed that by moving the wiring I disturbed something and maybe "unhooked" it from a grounding short.

Thanks for all the tips, I'll keep them in mind for the next time. and my one neighbor said I needed to rewire the trailer.....well not this time. Maybe they will help someone else that reads this thread.

 

[kwiktsi]

Wiggling a wire and it working again is not solving the problem, it's prolonging the inevitable .

 

[Seadoobuddy]

Wiggling a wire and it working again is not solving the problem, it's prolonging the inevitable .

:agree:....You are 100% correct, but if you can't find the problem in the first place, because all the wiring is inside the trailer frame you go with what you did and hope it doesn't happen again. At which time rewiring will have to be done.
I did find that the license plate light wire was squished between the bracket and the trailer....it had a flat spot but bare wire wasn't exposed that I could see. I untwisted it and re-routed it......maybe that was the problem.