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Diode Installation Instructions for Dinghy with Combined Tail Light Wiring

  • Before you begin the installation, ensure that your dinghy has a combined system, carrying the turn and brake signals on the same circuit
    • One bulb on each side of the vehicle carries the running lights, brake lights and turn signal functions behind a red lens
  • These instructions are rough guidelines of steps that need to be taken. The procedure varies from vehicle to vehicle.
  • Throughout the FAQ, the vehicle being towed will be referred to as the dinghy and the vehicle doing the towing will be called the tow vehicle

Wiring the Dinghy:

Diagram of Left-Turn Diode Connection

1. To Begin: Mounting and Grounding

  • Find a place on the front of the dinghy to mount the female end of the 4-way connector of the wiring harness from the diode kit
    • Strong bumpers can be a good connection point. If you are leaving the connector loose, ensure that it can be tied up out of the way and will not come in contact with anything hot
  • Ground the white wire with a ring terminal to a clean, metal surface somewhere on the vehicle frame
  • Route the rest of the 4-way harness along the vehicle frame to the rear of the dinghy, avoiding hot or moving parts
    • If possible, run the harness down the side opposite the exhaust outlet
    • Zip-tie the wire along the vehicle to secure it in place
    • Cut off the excess wire of the harness, including the 4-way connector, and leave adequate length to run the wires to the respective tail lights
    • Split the bonded wire, leading the yellow and brown wire to the driver side and the green wire to the passenger of the vehicle
  • Set wiring harness aside for a moment

2. Installation

Diagram of Running Light Jumper Wire

Inserting Jumper Wire Into a Spade Connector Twisting Together Jumper Wire and Running Light Circuit from Tow Harness

Locate the dinghy's factory running light and turn signal circuits and install a diode in-line with each. This process is outlined below. The diode installation is the same for each circuit.

  • Left brake and turn:
    • Locate the factory left-turn and brake wire on the dinghy using a circuit tester
    • Sever dinghy's left-turn signal and brake wire and install a diode in-line with the circuit
      • Using a spade connector, take the loose end of the factory wire coming from the front of the vehicle and attach it to one of the two prongs on the input side of the diode
      • Connect the loose end of the factory wire running to the tail light to the single prong on the output side of the diode. This reestablishes the dinghy's tail light circuit
    • Tie in the left-turn and brake circuit from the tow vehicle using a spade connector
      • Attach the yellow (left turn and brake) wire from the wiring harness to the remaining input prong on the diode
      • Tape up connections to secure them
  • Right brake and turn: Repeat left-brake and turn procedure on right side of the vehicle

Wirig Diagram for Wiring a Dinghy with a Combined Lighting System
  • Running lights:
    • Locate factory left-side running light wire on the dinghy and install diode, leaving one input prong open (temporarily hold off installing the wire from the wiring harness)
    • Next, locate factory right-side running light wire on the dinghy and install diode, again leaving one input prong open
    • Create a jumper wire to carry the running light circuit from the left-side running light to the right-side running light
      • Cut an extra length of wire that can extend from the left-side diode to the right-side diode
      • Twist together the loose end of the jumper wire on the left side and the brown wire from the wiring harness and insert the twisted ends into a spade connector
      • Connect both wires in the spade connector to the remaining prong on the right running light diode
    • Run the remaining loose end of jumper wire across and attach it to remaining prong on the input side of the right running light diode

To view a video installation of a similar installation, click here: Roadmaster Tow Bar Wiring Kit Installation Video

Connecting the Vehicles

A wiring extension cord must be run from the tow vehicle to the dinghy to connect their two wiring systems.

Tow Bar Wiring Extension Cord for Towing a Vehicle
  • Extension cord runs from the trailer connector at the rear of the tow vehicle, over the tow bar, and to the trailer connector installed on the front of the dinghy
  • There are two scenarios that could occur:
    • Your RV and dinghy have corresponding trailer connectors (e.g. They both have 4-way, female connectors)
    • Your RV and dinghy do not have corresponding trailer connectors (e.g. RV has a 7-way, female connector and the dinghy has a 4-way connector)
  • There are two ways to make ends meet:
    • Ensure that the tow vehicle and dinghy trailer connectors correspond, and purchase an extension cord that has the appropriate trailer connectors
      • Example: Both your RV and dinghy have female, vehicle-end, 4-way connectors. An extension cord with two 4-way, trailer-end, male connectors can connect the two wiring systems.
      • This may require replacing one or both of the existing trailer connectors on the vehicles.
    • Find an extension cable that has ends that correspond to each one of the vehicle connectors
      • Example: Your RV has a 7-way connector, and your dinghy has a 4-way. The connector cable will need to have a trailer-end, 7-way connector on one end and a 4-way, trailer-end connector on the other.
  • Before connecting the vehicles, attach the jumper cord to the tow vehicle and test the plug at the other end of the jumper cord to make sure the appropriate circuits are carried on the appropriate prongs

Note: Extension cords for towing a vehicle are unique. Unlike standard wiring adapters, both ends of the extension cord will have male, trailer end connectors. Ensure the extension cord you purchase for your setup has the appropriate trailer connectors on each end.

To see available extension cords and connectors click here.

Updated by: Raymond P.

Last updated: 6/29/18



Very clear and concise. Well done.

Etrailer Expert

Mike L.


Thank you very much, we're glad you found the article helpful!



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