Trailer light issues

[Eggflipper]

Here is the issue,
My buddy has a utility trailer that he bought new last year. He has a ‘24 ranger and my maverick is also a ‘24. Neither of our trucks will make the lights on the trailer work. He also has ‘22 f-250 that runs the trailer lights just fine. When I turn off my truck and exit the truck, the running lights will illuminate. It doesn’t appear to be an issue with the trailer. A meter on the 4 pin connector says everything is fine. It seems to be an “under load” type of issue. I know I get an error message on my truck when I hook it up. I’m wondering if it is maybe an undersized module. I do not have the 4000 pound upgrade on my truck.
Any thoughts?
Thank you.
sorry for the novella.

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[Mavster Mechanic]

Put extra lamps on the trailer or switch to incandescent bulbs.

I've read of this happening many times with all LED trailers.

 

[lm126027]

Put extra lamps on the trailer or switch to incandescent bulbs.

I've read of this happening many times with all LED trailers.

My snowmobile trailer has all LED lights, use the 4 pin and have had no such issue (2024 EB Lariat)

 

[Hot Runr Guy]

My snowmobile trailer has all LED lights, use the 4 pin and have had no such issue (2024 EB Lariat)

Same with my boat trailer. All LED's and no problem w/2K 4-flat connector.

HRG

 

[Hot Runr Guy]

Here is the issue,
I know I get an error message on my truck when I hook it up.

What error message are you getting?

HRG

 

[BlueSpec1]

Saw one person's trailer tow issue:

"The fix was to add and tie in a second ground on the vehicle.
Seemed strange to have two grounds on the same circuit but am out of ideas several trips to ford and the trailer manufacturer.
And getting nowhere, I add a 6 inch 14 gage wire from the crash bar receiver hitch to the back of the 4 pin and 7 pin connector leaving the tiny 18 gage wire still in the system.
Low and behold it works."

 

[Hot Runr Guy]

Saw one person's trailer tow issue:

The fix was to add and tie in a second ground on the vehicle.
Seemed strange to have two grounds on the same circuit but am out of ideas several trips to ford and the trailer manufacturer.
And getting nowhere, I add a 6 inch 14 gage wire from the crash bar receiver hitch to the back of the 4 pin and 7 pin connector leaving the tiny 18 gage wire still in the system.
Low and behold it works.

@BlueSpec1 , refresh my memory. Did you add the 7-pin connector to yours? I see that the OEM harness feeding the 7+4 socket has a 2nd ground wire incorporated.

HRG

 

[BlueSpec1]

@BlueSpec1 , refresh my memory. Did you add the 7-pin connector to yours? I see that the OEM harness feeding the 7+4 socket has a 2nd ground wire incorporated.

HRG

I haven't.
It's too hot/humid for me to do truck stuff outside.

The harness for the 7+4 Pollak does have two 14 Awg at the Molex 2x6 connector for ground that are spliced inside the harness to 10 Awg at the C4099 connector:

Molex 2x6 Male to C4099 7+4:

C4099 7 Pin to 7+4 Pollak:

The C439 2x6 Molex male connector to 2K 4 Pin Flat has one 14 Awg for ground.

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