How to wire tow bar electrics

Written by joe faulkner-edwards
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When using a tow bar, all lights on the rear of the vehicle or trailer being towed must be operated from the lead vehicle Without correct electrical function, neither vehicle will be road legal. The majority of tow bars use two electrical systems. A 12N system is used for standard vehicles and trailers, whereas a 12S system takes into account the auxiliary power needed for caravans and motorhomes. Both feature a 7-pin connector and use the same colour-coding system. Know which wire connects to each pin to save on auto-centre fitting fees.

Skill level:
Moderate

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Things you need

  • Vehicle specific tow bar wiring kit

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Instructions

  1. 1

    Insert the yellow wire from the vehicle into the pin labelled "1", found on the tow bar. Insert the yellow wire from the trailer or motor home into pin 1 of the rear connector on the tow bar. With 12N systems, this powers the left blinker (indicator). With 12S systems, this powers the reversing lights.

  2. 2

    Insert the blue wire from the vehicle into the pin labelled "2", positioned on the front of the tow bar. The blue wire from the trailer or motor home connects to the second pin on the rear connector. With 12N systems, this powers the fog lights. With 12S systems, this powers the battery.

  3. 3

    Insert the white wire from the vehicle into the pin labelled "3". Insert the white wire from the trailer or motor home into pin 3 on the rear connector. For both systems, the white wire operates as the earth wire.

  4. 4

    Insert the green wire from the vehicle into the pin labelled "4". Insert the green wire from the trailer or motor home into pin 4 on the rear connector. With 12N systems, this powers the fog lights. With 12S systems, this is the power feed.

  5. 5

    Insert the brown wire from the vehicle into the pin labelled "5". Insert the brown wire from the trailer or motor home into pin 5 on the rear connector. With 12N systems, this powers the right side lights. With 12S systems, this powers the tail lights and any sensor systems on the motor home.

  6. 6

    Insert the red wire from the vehicle into the pin labelled "6". Insert the black wire from the trailer or motor home into pin 6 on the rear connector. With 12N systems, this powers the break lights. With 12S systems, this powers the fridge in the caravan or motor home.

  7. 7

    Insert the black wire from the vehicle into the pin labelled "7". Insert the black wire from the trailer or motor home into pin 7 on the rear connector. With 12N systems, this powers the left sidelights. With 12S systems, this operates as the earth for the fridge.

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