Trailer lighting module fault

[Prickly Pear]

Hooked up my utility trailer to the Mav for the first time and received the subject fault message as soon as I got out on the road. Turned around and dropped off the trailer as the message was persistent and I didn't want to burn anything out. I have hauled the trailer many times with my Ranger and other than the turn signals blinking rapidly I never had a problem and the lights all seemed to work.
I checked the 4 pin connector with my multimeter and had zero resistance between the white and colored wires, so all looked good. Then I check the continuity between colored wires (green, yellow, brown) and they all show zero resistance, which I don't think is supposed to happen. This sounds more involved than the usual bad ground and maybe I have a short between circuits? Any suggested first places to check?

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[B. Adams]

You should see a few ohms of resistance in a dead short. 0 ohms means an entirely open circuit, in other words, no short. The fact that you're getting 0 ohms between all conductors indicates to me that either your connector isn't connected to anything, or your trailer lights are probably LED.

LED's on their own don't respond to a continuity test like incandescent lamps do. I've never dissected one, but trailer lights probably have active circuits in them, which you won't be able to test with a basic multimeter. An easier test would be to hook up a battery or 12v power supply to the 4-way plug and see if the lights come on like they should.

I'm guessing it's a bad ground or a corroded connector. Those 2 things account for 99.9% of trailer light issues, in my experience.

 

[Prickly Pear]

I'm probably not explaining myself correctly. I'm using a Fluke meter that beeps when it detects a continuous circuit. I not only get a beep when testing between the ground and Brown, Yellow, or Green, I also get a beep when I test from green to yellow, green to brown, and Yellow to Brown. I am pretty sure that isn't supposed to happen. Does that mean I have a short or is that something you will see with LED lights? I thought those 3 circuits were supposed to be independent?

 

[Prickly Pear]

You should see a few ohms of resistance in a dead short. 0 ohms means an entirely open circuit, in other words, no short. The fact that you're getting 0 ohms between all conductors indicates to me that either your connector isn't connected to anything, or your trailer lights are probably LED.

LED's on their own don't respond to a continuity test like incandescent lamps do. I've never dissected one, but trailer lights probably have active circuits in them, which you won't be able to test with a basic multimeter. An easier test would be to hook up a battery or 12v power supply to the 4-way plug and see if the lights come on like they should.

I'm guessing it's a bad ground or a corroded connector. Those 2 things account for 99.9% of trailer light issues, in my experience.

The lights worked fine, but the trailer control module was not happy. You were right about the ground though - that was the problem. My trailer lights were grounded to the frame, and the plug likewise was connected to the frame. I checked the spot bonds at the light and they were good. Then I remembered my trailer is a folder, even though I never fold it up. I apparently had high resistance across the hinge joint. I just ran a ground wire back to the rear of the frame and everything is working fine. I have not hooked it up to the Ranger yet but I"m betting my rapid turn signal problem will be gone.

 

[AF Blue]

I have hauled the trailer many times with my Ranger and other than the turn signals blinking rapidly I never had a problem and the lights all seemed to work.

Trailer have all LED lighting?

The lights worked fine, but the trailer control module was not happy. You were right about the ground though - that was the problem. My trailer lights were grounded to the frame, and the plug likewise was connected to the frame. I checked the spot bonds at the light and they were good. Then I remembered my trailer is a folder, even though I never fold it up. I apparently had high resistance across the hinge joint. I just ran a ground wire back to the rear of the frame and everything is working fine. I have not hooked it up to the Ranger yet but I"m betting my rapid turn signal problem will be gone.

Glad you were able to fix it.
Thank you for sharing your fix.
I am sure someone will encounter the same or similar.

 

[Prickly Pear]

Nope, all standard bulbs. I was also thrown by continuity between colored wires, but I guess that is normal.
FYI if you google continuity between colored wires on a trailer the AI says it should not happen. Guess that shows what AI is worth! Look out, here comes skynet!

 

[OleFordGuy]

Nope, all standard bulbs. I was also thrown by continuity between colored wires, but I guess that is normal.
FYI if you google continuity between colored wires on a trailer the AI says it should not happen. Guess that shows what AI is worth! Look out, here comes skynet!

HA, yep, my opinion of AI at this point is it's just gathering whatever shit it finds out there and assembles a answer. Garbage In/Garbage Out. I'm an old fart so I'm just leery of new experimental stuff.

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