Bike Trailer - Light Wiring Issue.

[EvilBetty]

I bought a used trailer a while back to use as a bike hauler.  I can't remember if the lights have ever worked right but last week the passenger side wouldn't come on at all, so tonight I decided to tear into it.

This is a simple 3 wire trailer light kit, tongue ground.

3 wires run to the drivers side light.  The green does not connect and continues to the passenger.  The brown is connected to the drivers side but also continues to the passenger side.

Brown is TAIL
Green is PASSENGER BRAKE / SIGNAL

Ok... so here's the deal.  The light wasn't working at all because of a bulb fitment issue.  After putting the bulb in right side up (lol) and bending the rails out a bit the tail light works fine.

The passenger side blinker however, does not.



I took off the housing and measured voltage from the wires, grounding at the trailer.  With the blinker on.  The brown was a solid 11+ volts, and the green was bouncing around as would be expected.

I measured continuity on each bar and they were not connected.

I reinstalled the housing, and measured the same voltage readings above, measuring from the bars and the ground on the bulb retainer.

I used a 9V to test the bulb... working fine.

So then I reinstall the bub.  Still no blinker.  Check voltage at the TAIL bar... still 11+ volts.  Check at the BRAKE/SIGNAL bar, and NOTHING.  0.00V.  Take the bulb out... measure again... bouncing again.  Put the bulb back in... NOTHING.

I  fought this for 2 hours tonight... I was about to just install new LED lights, but I couldn't let this POS beat me.

Any ideas?

[Mustang]

it's ground they don't like tounge ground
run a ground wire from the vehicle and I bet your problems are gone
or the flasher in your pull vehicle needs to be a heavy duty for the xtra load of the trailer bulbs
my bet is ground though

[EvilBetty]

Yeah I've been looking at that cut off wire on the harness knowing I should drill a whole on the tongue for it.

It's so weird though, the driver side is working fine... blinker too.  Just this damn passenger side giving me fits.  And everything measures out fine until I put the bulb in, but I've looked everywhere.  I can't find anywhere were it could be shorting out.

I've got to pick up the riding mower tonight so I'll tap a ground on the trailer before I put it all back together.

[EvilBetty]

So I get home and need to go pickup my mower.  I decide to throw it all together and not mess with it till I get down there and just buy a new passenger tail light.

As I'm putting it all back together I test it one more time... you know, in case it fixed itself... and it hasn't.

As I'm fitting the lens I accidentally let the screwdriver touch the screwdriver inside shorting the TAIL and BRAKE/SIGNAL 12+ bars that connect to the nubs on the back of the bulb.  Small spark, and my blinker starts working....

This baffled me... it didn't make any sense.  Though I should have just left it alone, I took it all apart again to find out WTF was going on... I couldn't find anything amis or that would explain why the shorting of the bars resurrected the blinker.

I went and picked up the mower.... came back home... picked up roll-away basketball goat (should have taken a picture... that looked funny being hauled behind my truck) took it to my brothers sporting the hazzards... never had a malfunction.  Picked up a new taillight anyway... and a new wireing harness with a ground... so of course it won't fail for the life of the trailer now.