8/8/2019 Towbar Wiring Guides

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Towbar Wiring Guides

Listed below are some basic 12N and 12S type wiring diagrams that will help in vehiclewiring for both road lights and caravan internal electrics.

Alternatively, we are willing and able to look at any wiring problem here at our workshops.

WIRING DIAGRAM FOR 12N TYPE 7-PIN Black socket or plugfor vehicle road lights

Colour   Terminal  Purpose Looking at the Socket towards the plug.Looking at the Plug towards the socket. 

Yellow  1 (L)  LH Indicator  

Blue  2 (54G)  Rear Fog Light (or Aux.) 

White  3 (31)  Earth 

Green  4 (R)  RH Indicator  

Brown  5 (58R)  RH side Light

Red  6 (54)  Stop Lights 

Black   7 (58L)  LH Side Light 

WIRING DIAGRAM FOR 12S TYPE 7-PIN Grey socket & plugfor caravan & trailer interior power.

Colour   Terminal   Purpose Looking at the Socket towards the plug.

Looking at the Plug towards the socket 

Yellow 1  Reverse Light Blue 

2 Pre 1/97

2 Post 1/97 Battery Charging or Power 

White  3  Earth 

Green  4  Power or Battery Charging 

Brown  5  Warning Light for pin 1 

Red  6  12V Refrigerator  

Black   7  Spare

WIRING DIAGRAM FOR 12N TYPE 7-PIN INCLUDING REAR MOUNTED

AUDIBLE BUZZER for most cars that do not require bulb failure bypass relays

WIRING DIAGRAM FOR SELF SWITCHING RELAY ON 12S SOCKET 

8/8/2019 Towbar Wiring Guides

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WIRING DIAGRAM FOR DOUBLE RELAY ON 12S SOCKET 

TROUBLE SHOOTING 

FIRST: Check and test the fuses on all circuits 

SECOND: Ensure that there is a good clean EARTH connection to the vehicle body, the

7-pin socket, the trailer 7-pin plug and the trailer lamp units.  

If one circuit does not function check and test the fuses, check and test the bulbs.If fuses continue to blow, calculate that the fuse is the correct size for the load on the circuit

(Watts/Volts = Amps eg 4x21w / 12v = 7A). The fuse rating should be appr oximately twice

the load to allow for surges.

Look for a ³short circuit´ ± bare wires or contacts touching Earth along the loom, the socket,

the plug or in the lamp units.

If any bulbs flash or dim out of sequence, check ALL the earth connections.

Other checks you can do include:

1.  Clean off all paint, dirt or rust from around the earth point, fix a ring tag to the white

wire from the 7-core and fix securely to the earth point, smear with petroleum jelly.2.  Clean the bulb contacts and holder.

3.  Test the other six wires for continuity across the connectors and to the lights.4.  Test the screw connections in the socket, if there is any sign of corrosion replace the

socket. Discard any socket covers or rear seals as these only promote corrosionthrough condensation, ensure drainage from the socket. Ensure that the 7-core is lead

through grommets in metal surfaces and prevent chaffing at any point. Clip the 7-core

 back to one of the socket screws with a P-clip.

5.  Check and clean the individual pins in the socket, spreading the male pins slightly.