M1101 M1102 Trailer Wiring Issue

I bought a M1102 (2007 Schutts) recently and my first project is getting the wiring figured out.
I bought the 7 pin military to civilian harness and followed the instructions from Expedition Supply. I also found similar instructions at https://referenceonly.wordpress.com/m1102/

The wiring instructions stated to put the GREEN wire to #21. There was not a #21, but there was a #21-498 on my trailer. I did install to #21-498.
After installation, I tested out the lights. The LED "Truck-Lite" brand lights (10v-30v) worked on the curbside only, 2 lights. All other marker lights did not work.
Is it possible that the rest of the LED marker lights (both red and yellow) are burned out?

My next step is to use a voltage meter to see if any current is going to these lights.

Any help or suggestions are appreciated.


No replies yet... maybe I’m doing this wrong.
We out to test the lights with multi-meter tonight and now about half the LED lights are working. I think I’ll order several of the replacement bulbs and try them out.

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My limited experience with led lights is that they simply do not last anywhere near the claims. I know there are many different kinds & some are supposed to be far superior to others, but I have seen many a brand new vehicle with leds out.

So yeah there's that. The next thing I would check is the grounds, especially on an aluminum trailer. Dissimilar metals promote corrosion & if steel wire terminals were used, it could be an issue. Next I would check for wire chaffing or breaks, it is a military trailer after all & out of the 350 person unit that I was in, only about 5 of us took really good care of our vehicles.

Good luck.

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There is a good chance you have a ground problem.

Are these lights grounded to the frame?

And BTW, I've had LED trailer lights going strong since 2013. Nary a flicker.