Turn Signal Issue

[JustWandering_U]

I am experiencing an issue that I was hoping was simple ground issue. We check the lights before every trip and they were working fine two weeks ago then last Saturday we were doing our pre-trip and the issue was first noticed.

Problem: When I turn on either turn signal, both trailer signals blink (as if the hazard lights are on), while the correct light blinks on the truck.

Troubleshooting so far:
1) I used a test light to verify the plug on the pickup is performing properly
2) I used a test light to verify the wiring harness on the trailer is performing properly
3) I removed one trailer tail light, ran a jumper wire from the white (ground) wire to the frame

I would like to find a wiring diagram, but Google has been no help. Do any of you have suggestions?

[BarabooBob]

Have you tested your 7 pin connector with a test light? This will narrow your search and if the truck connector is good, you are half way to finding your problem.
SUN Heavy Duty 7-Way Trailer Light Circuit Connector Tester w/LED 7 PIN Round RV Blade Electric Wiring Adapter
I have test lights for 4 pin and 7 connector style trailer plugs. I would not be without them.

[Campfire_Time]

Ask this question on a Dodge forum. It might be the flasher unit. Some years back I had an issue like this on my old Trailblazer. I even replaced the factory 7 pin outlet. I ended up going on the trip with the lights not functioning right. Keep in mind that without the trailer attached the truck lights worked fine.

When I got back I did a bunch of research and found out it was the flasher unit in the truck that went bad. It was tied into the entire running light/signal system and could no longer handle the extra load of the trailer lights. But the behavior was just like a bad ground. I wasted hours trying to track it down only to find out it was an easy fix.

[bob213]

Can't offer any more to fix problem but I hope you track it down. I didn't know that people still use their turn signals ;)...they sure don't where I live!

[Lakeland_Bob]

I agree, check the bulbs. Earlier this past year I installed a set of LEDs in my trailer signal/stop lights. For some reason (probably cheap bulbs) both sides lit up whenever a signal was selected. Went back to regular bulbs and all is well.

[wnjj]

If you pull the bulb from the side you’re trying to operate does the wrong side still flash?
E,g, pull the left bulb and then turn on the left turn signal. If that stops the right bulb from flashing there’s a bad ground to the light fixtures. If the right side still flashes there’s a short between left and right turn wires somewhere between the plug and lights,

[enblethen]

It could be a hang nail in non-molded connector' but doubtful

[JustWandering_U]

enblethen wrote:
Did you change the lamps? Possible that a filament is broken and fallen on the other filament.
Adding ground as you indicated would correct ground issue in trailer. Did you clean ground in truck?

I haven't changed the bulbs/lamps.

I haven't checked the ground on the truck, I'll do that tomorrow in daylight. Thanks!

[edit]You know, we did go driving on some 4X4 trails between the last time we pulled the trailer and the point in which it started acting up. Hopefully it's the truck ground.[/edit]

[enblethen]

Did you change the lamps? Possible that a filament is broken and fallen on the other filament.
Adding ground as you indicated would correct ground issue in trailer. Did you clean ground in truck?

[JustWandering_U]

Wouldn't grounding one of the lights to the frame fix the issue if it was a simple grounding problem?

[JustWandering_U]

pull the ground wire off where its attached to the frame clean to bare metal.

Pulled ground-to-frame connection, wire brushed both the connector and the frame, re-assembled.

99% of light problems are ground related.

I know, right? That's what's frustrating...it's GOT to be something simple.

I would check the trailer connection for 2 wires touching and the tow vehicle plug again also if they ore touching the meter will read voltage on both signals connection at the same time. Voltage is getting to the other side some way.

Checked all wires to the plug in the truck and at the point of connection for the wiring harness. Nothing is touching there.

Voltage is getting to the other side some way.

I agree. It's got to be somewhere after the wiring harness at the trailer. I completely un-wired the harness from the trailer and tested the wires individually. All wires tested good. When I wired it back up, the issue resurfaced.

I guess the best thing at this point is to start chasing wires. 😞

[rhagfo]

I would check ground pin on both the TV and Trailer, should be zero oms reading between connector ground blade and that vehicle frame!

[donn0128]

Guaranteed grounding issue.

[jrobert01]

I would check the trailer connection for 2 wires touching and the tow vehicle plug again also if they ore touching the meter will read voltage on both signals connection at the same time. Voltage is getting to the other side some way.

[midnightsadie]

X1 everything did work,, pull the ground wire off where its attached to the frame clean to bare metal. 99% of light problems are ground related.