Strange Trailer Light Problem

[mdhave]

Lights and Brake Lights work fine. Signal behavior below:

Left blinker works with lights on or off.
Right blinker does nothing with lights on (maybe the faintest pulse on both lights).
Right blinker blinks BOTH lights when the lights are off.

The right blinker works if the wires are not connected to the other (left) light.

Here's what I have checked:
1. Getting correct voltages on the 3 pins of van (lts, left & right blink)
2. Verified voltages at the taillights: brown (light), green (blink), yellow (blink) all have correct voltages. Wires are not crossed--no connectivity between brown/green or brown/yellow.

Other info:
Ground from the van to the trailer is via a wire and bolt on the trailer.
The left light is new and so is all the wiring.

Would a faulty light (on either side) explain this behavior?

Thanks in advance for suggestions. I am pulling my hair out!

[Shellback]

I've had a filament burn out in a bulb, which then dropped across to the second filament, which back feeded current to the other light. Have you replaced the bulb?

[yarcraft91]

Lights and Brake Lights work fine. Signal behavior below:

Left blinker works with lights on or off.
Right blinker does nothing with lights on (maybe the faintest pulse on both lights).
Right blinker blinks BOTH lights when the lights are off.

The right blinker works if the wires are not connected to the other (left) light.

Here's what I have checked:
1. Getting correct voltages on the 3 pins of van (lts, left & right blink)
2. Verified voltages at the taillights: brown (light), green (blink), yellow (blink) all have correct voltages. Wires are not crossed--no connectivity between brown/green or brown/yellow.

Other info:
Ground from the van to the trailer is via a wire and bolt on the trailer.
The left light is new and so is all the wiring.

Would a faulty light (on either side) explain this behavior?

Thanks in advance for suggestions. I am pulling my hair out!

Hmmm. You checked for a short brown/green and brown/yellow. You say the right blink works if the left blink is disconnected, but you don't say if you checked for a green/yellow short. That's worth checking if you have not. As mentioned earlier, a goofed up bulb is possible, but so is chafed insulation on the wiring. I once had mice get in the trailer frame and chew insulation off 6' of the wiring harness. You wouldn't believe the wierd stuff those trailer lights would do.

Also worth checking the ground connection at the right light. Good luck.

[perchjerker]

I agree with Shellback

try replacing the bulbs

start with the simple stuff first

[corvette744]

Lights and Brake Lights work fine. Signal behavior below:

Left blinker works with lights on or off.
Right blinker does nothing with lights on (maybe the faintest pulse on both lights).
Right blinker blinks BOTH lights when the lights are off.

The right blinker works if the wires are not connected to the other (left) light.

Here's what I have checked:
1. Getting correct voltages on the 3 pins of van (lts, left & right blink)
2. Verified voltages at the taillights: brown (light), green (blink), yellow (blink) all have correct voltages. Wires are not crossed--no connectivity between brown/green or brown/yellow.

Other info:
Ground from the van to the trailer is via a wire and bolt on the trailer.
The left light is new and so is all the wiring.

Would a faulty light (on either side) explain this behavior?

Thanks in advance for suggestions. I am pulling my hair out!
Why is the left light new and all wiring-did you have this problem and then replace them,or have the problem right after replacing.If its not the bubl and you have a good ground then you have a bad rear light assy.I would assume if it were a short to ground you would be smoking wires or blowing fuses.

[mdhave]

Thanks to everybody who responded. For posterity, we messed around with the bulb in the right trailer light for awhile and got some different results and eventually replaced the whole right taillight assembly, which fixed the problem.

Next problem I have will result in new LEDs for the whole trailer!

[Bigfishhunter]

I switched over my whole assembly to LED's and have had no problems whatsoever in 3 years.