Every dealer I checked advised that the factory trailer light wiring harness is no longer available for the 1999 ML 430.

1.) Does anyone know a source for a new or used factory plug-in harness?

There are links to many after market hitches and wiring kits. Here is one that identifies a hitch and harness for the 1999 ML 430: http://www.hitchestogo.com/Mercedes_Hitches.htm

I have printed the instructions for the wiring kit they recommend and the color coding for the wires, etc is all very clear. What's not clear is how to connect to the wiring system of the ML 430. My factory DVD does not have a wiring diagram. Here is the link to their instructions:
http://www.hitchestogo.com/Instructions/N119186.pdf

2) What is the best way to make the wiring connections into the tail lights, brake lights, and turn signal lights of the ML ? I have the cover off in the inside left rear. The plug for the factory harness is right there. What are the correct next steps in making connections?

Thank you very much,

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Jim Herold--Current: 1987 190E 16V, 1999 ML 430--Past: 1971 280 SL, 1972 250