Wiring a Motor Home with Converterd Wiring to Tow a Vehicle with Separate Turn and Brake Signals

Updated 02/23/2010 | Published 02/22/2010

Products Featured in This Question

Roadmaster 4-Diode Universal Wiring Kit for Towed Vehicles - 4-Way Flat Connectors

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$86.90

Roadmaster Bulb and Socket Tail Light Wiring Kit for Towed Vehicles - Incandescent

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$83.99

Question:

motor home has tail light converter and seperate turn signals.Towed vehicle has seperate turn signals and brake and tail light on one double filament bulb I am a bit confused on the wiring of towed vehicle diodes how many . I am told with the converter on MH it converts my towed vehicle to using tail and stop lights as one with diodes and no diodes on turn signals . Then iwas told by another party to remove converter and wire direct no diodes can you please help or advise.

asked by: John T

Expert Reply:

Lets start from the beginning. There are several ways to wire a towed vehicle and motor home. All of the suggestions you have considered will work, except wiring directly without diodes. Here is what I think. Your motor home has a connector at the back that is already converted. In my opinion there is no reason to remove the converter because you may need to tow some other item at some time in the future and the converter will be needed.

I would wire the vehicle with a separate bulb system, like the RoadMaster Tail Light Wiring Kit with Bulbs, item # RM-155, if there is enough room in the red area of the taillight housings to accept an extra bulb. This wiring system requires that you drill a hole in the back side of the tail light assembly, to insert the new bulb and socket, but bypasses the vehicles wiring avoiding any issues with splicing into the vehicles wiring or warranty. The new bulb will simply function like a trailer tail light bulb in the cars tail light assembly.

If there is not room to install a bulb and socket in the vehicles tail light assembly then I would use a diode system like the Roadmaster Universal Hy-Power Diode Wiring Kit, item # RM-154. You will need to wire the system with 4 diodes. The yellow wire will go from the trailer connector to the diode inline with the left brake circuit. The green wire will go to the diode inline with the right side brake circuit. The brown wire is routed to the diode inline with the right side tail light circuit and a jumper is routed from the brown wire on the right side before the diode to the left side diode inline with the left tail light circuit. I have linked a picture below of the wiring that will be needed if you choose to use diodes. This system will then use your brake light bulbs as both brake and turn signals and your tail lights will function normally.

The third brake light on the towed vehicle is not needed and will not function unless an extra diode is used and the third brake light wiring is spliced into. It is usually very difficult to access the third brake light wiring on most vehicles. Let me know if you run into trouble wiring we are here to help.

expert reply by: Robert G