umm , both signal lights flashing on trailer - Diesel Forum

weraracer · 03-25-2006, 12:54 PM

so since my factory harness seems to have bugs in it, i decided to instal a seperate system off my truck lights. so i ran the 4pin set up, hooking the tailight wire to the driver tailight, and the driver signal to the driver signal. then i hooked the pass. signal to the pass tailight wire (for signal), and then the ground.

hook up trailer, and tailights work fine. and the signal light will work fine if the taillights are OFF, but with the tailights on and then the signal at the same time - i get both sides flashing - but only on the trailer - the truck works fine.

so i test the power at the harness connector and everything seems fine there - so it would appear that the signals that the truck is sending is good for all the lights. but yet the trailer is wacked. any ideas on how to fix this???

as far as the trailer it has the ground hooked up, a brown and green running to the pass side, and a brown and yellow to the right. between trying to figure out/fix the factory harness and this, this simple thing has turned in a PITA

weraracer · 03-25-2006, 03:07 PM

ok after a bit of trial and error, it seems the lights were grounding out and sending a signal accross the trailer to each other. anyway the lights wrok fine off the trailer, BUT now when i have the park lights on and i hit the brakes the lights go out. the brakes work fine without the park lights on though? any ideas??

Believer45 · 03-25-2006, 03:58 PM

Sounds like

1) your ground at both taillights is bad (it will ground for the taillights through the brake light filament but when you try to light the brake lights they lose ground and go out. When you try to light the brake lights when the running lights are off what you are actually doing is lighting the taillights, not the brake lights)

or 2) you have a bad ground between the trailer and the tow vehicle.

Dave / Believer45

weraracer · 03-25-2006, 04:20 PM

i am LOST on this! i cannot reconnect the taillights to the trailer, when i do, the signal lights get all screwed up (both lights flash). when i hook up 1 light, it will work fine (brake, signal tail all work) but when i hook up both it goes all to crap.

it is amazing but this also happens... when i take the wires and disconnect them from the trailer lights (so now they are only hooked up at the harness at the hitch) the wires for the right line will blink my test light when the LEFT signal is on! it isnt even attacthced to anything! and once more when i test the output from the truck the output ISNT TELLING THE WIRES TO BLINK! but on the other end of the very same wire IT IS!
i swear to god i am not an idiot, and i know this should be easy, and no doubt its something very simple - but for the life of me, i am lost.

oh and the ground is connected at the harness and on the truck side it is grounded as well. could the ground on the truck not be good enough? [img]/ubbthreads/images/graemlins/shrug.gif[/img] [img]/ubbthreads/images/graemlins/crazy.gif[/img] [img]/ubbthreads/images/graemlins/depressed.gif[/img]

BEECHBM69 · 03-25-2006, 06:33 PM

I sounds very much like a ground problem as Believer 45 said. I don't know what kind of trailer your dealing with, but on my travel trailer, the ground was attached to the frame near the tongue. The light was grounded through the aluminum skin of the trailer. Frame and skin weren't contacting very well and I had much the same scenario you describe. I ran a ground wire straight to the skin and now all is well. See where your ground from the trailer plug actually attaches to the trailer and go from there. Good luck.

Dan

weraracer · 03-25-2006, 09:03 PM

fixed! i ran a wire from each light mount to the ground at the front and voila! we have lights. thanks for the replies.

j_apetersen · 03-25-2006, 10:37 PM

[ QUOTE ]
so since my factory harness seems to have bugs in it, i decided to instal a seperate system off my truck lights. so i ran the 4pin set up, hooking the tailight wire to the driver tailight, and the driver signal to the driver signal. then i hooked the pass. signal to the pass tailight wire (for signal), and then the ground.

hook up trailer, and tailights work fine. and the signal light will work fine if the taillights are OFF, but with the tailights on and then the signal at the same time - i get both sides flashing - but only on the trailer - the truck works fine.

so i test the power at the harness connector and everything seems fine there - so it would appear that the signals that the truck is sending is good for all the lights. but yet the trailer is wacked. any ideas on how to fix this???

as far as the trailer it has the ground hooked up, a brown and green running to the pass side, and a brown and yellow to the right. between trying to figure out/fix the factory harness and this, this simple thing has turned in a PITA

[/ QUOTE ]

You have a turn signal hooked to ground and the ground hooked to turn.Check the ground pin on the bulb and make sure you have it hooked to ground. eather that or you have a bad bulb.

JimTJr · 03-27-2006, 08:37 PM

You simply have a ground problem, That will drive you loco on a trailer. I BET you have the wires hooked up correctly. BUT the ground is absolutely the most important thing. Those electrons will go all over without a good ground!! LOL
Make sure the lights are grounded to the trailer good. Make sure the trailer has a good ground. Run the wire ground thru the plug. Hook to the trailer on the trailer side,,and the frame on the truck.
Do NOT trust the ball to be your ground,,,,,(Works many times,,but when it doesnt,,,it will drive you nuts)