Now for the difficult part: Tail Lights.

Tail lights are difficult for several reasons. Isolating the circuit from feedback using a diode will require splicing or running new wires to several locations.
Typically installing a diode at one rear light fixture will only power 1 light. There are some options to operate both lights.
You can rewire the rear light from the other side and splice in to that diode, or you can use 2 diodes.
The next issue is the license plate light. By law you are required to have a working license plate light.
Most technicians do not wire the license plate light. Remco does not include directions in their lighting kit nor does any other company that I’m aware of.
I have talked to Remco’s installers and they do not wire that circuit.
The only way to make that license plate light work correctly is to cut the original feed to the socket and run a new wire to the location of the diode.
I usually install the tail light diode on the driver’s side. Remove the tail light fixture.
Cut the wire feeding the right tail light. Cut the wire feeding the license plate light. Insulate both ends that fed the original circuits with electrical tape or a connector.
I like to use a butt connector and dielectric grease so the wire and circuit will still be in good condition is ever reused.
Attach equal size wire to the bulb side of each light. Run the new wires to the driver’s side tail light.
You can use a terminal that will splice 3 wires together. I usually use a yellow female spade terminal. The spade will attach to the diode.
Yellow is for 10 gauge wire which should accommodate the 3 small wires.  Cut the original wire feeding the taillight bulb on the driver’s side.
Install a terminal to the harness side of the wire and attach it to the input side of the diode.
Install a terminal on the brown wire from the trailer wire harness you installed and attach it to the other input side of the diode.
Install the yellow spade terminal to the wire feeding the left tail light bulb, and the 2 wires you routed to the bulb area.
Attach this terminal to the output side of the diode. This will power all 3 lights from either the vehicles harness or the trailer harness you installed.

You can now install the front trailer connector. Pull the excess wire through the trailer connector. Leave a few inches of extra wire. Install the wires to the connector.
If using a round 4 wire connector there is no standard wiring pattern.
I use this type connector with a coiled cord if towing with lights only (no lube pump, braking unit or charging system).
You will probably need to install a mating 4 wire round connector to your RV. You can simply match your wires to each since there is no industry standard.
If you have a lube pump you will be using the 6 wire connectors and coiled cord supplied from Remco. Their wiring schematic is in the instructions.
If you need additional wires, I recommend using a 7 way connection. 7 wire harnesses can be purchased from an auto parts supplier.
You will need to cut it to the proper length to run between the RV and towed vehicle, then attach the connectors to it.
I usually tie strap the cord to the tow bar, then simply disconnect the end from the towed vehicle when not in use. If you need more than 7 wires, use 2 – 4 wire coiled cables and sockets.

Caution: I recommend not connecting your harness between the RV and towed vehicle until you are finished connecting your tow bar and have turned off the vehicle and all of its lights. In some vehicles the light circuits pass through one of the computers and it may be possible to damage this circuit if there are 2 inputs at the same time.

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