Trailer Lamps: Description and Operation

Trailer Socket

DESCRIPTION

Introduction
The type of trailer socket fitted to the vehicle is dependant upon market. United Kingdom (UK) vehicles are fitted with either a 12N or 12S socket. The 12N trailer socket supplies power for lighting functions only. The 12S trailer socket provides the same lighting feeds plus the additional power feeds required for caravan accessories.

The following table shows the pin allocation of the 12N/12S trailer socket.

12N 12S Trailer Socket

Pin Function
1 Reversing lamps
2 Spare
3 Ground for lamps
4 Interior lamps and charging
5 Spare
6 Fridge
7 Ground for fridge

European vehicles are fitted with a 13 pin trailer socket. The pin allocations for this socket are shown in the following table.

13 Pin Trailer Socket

Pin Function
1 LH turn signal indicator
2 Fog lamps
3 Ground for pins 1, 2, 4, and 8
4 RH turn signal indicator
5 RH tail lamp and number plate lamp
6 Stop lamps
7 LH tail lamp and number plate lamp
8 Reverse lamps
9 Constant battery feed
10 Ignition feed
11 Ground for pin 10
12 Coding for trailer
13 Ground for pin 9

North American vehicles are fitted with either a 4 or 7 pin connector. For pin allocation details, contact your local supplier.

NOTE: The pin allocations shown in the previous tables are for the connection between the vehicle and the trailer. They are not the pin-out details of the vehicle harness connector.

OPERATION

12N 12S

Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 11E and fusible link 18E (C0632) on an R wire. Both are located in the Battery Junction Box (BJB). Fusible link 18E (C0570) provides a constant battery feed to the Central Junction Box (CJB) and fuse 8P (C0583) on an NS wire.

Fuse 8P (C0585) is connected to fuses 1T and 2T within the trailer fuse box (C1875) by a GN then P wire. Fuse 1T (C1875) provides a constant battery feed to the trailer socket relay (C2937) on a U wire. Fuse 2T (C1875) provides a constant battery feed to the trailer pick-up (C1381) on a UK wire.

Fusible link 11E (C0570) is connected to the ignition switch (C0028) by an N wire. When the ignition switch is in the ignition position, current flows across the switch (C0028) to fuse 22P of the CJB (C0582) on a Y wire. Fuse 22P (C0585) provides an ignition feed to the trailer socket relay coil (C2937) on an R wire.

Trailer Socket Relay
The trailer socket relay coil (C2937) is provided an ignition feed by fuse 22P of the CJB (C0585) on an R wire. The relay coil (C2937) is provided a ground path on a B wire. The energised relay (C2937) provides a feed to the trailer pick-up (C1381) on an RW wire.

Tail and Number Plate Lamps
When the lighting control switch is turned to the side lamp position, the energised side lamp relay provides a feed to fuse 14P, which is also located in the CJB. Fuse 14P (C0583) is connected to fuse 5T and fuse 6T of the trailer fuse box (C1875) by an N then RO wire. Fuse 5T (C1875) provides a feed to the trailer pick-up (C1382) for the RH tail lamp on an N wire. Fuse 6T (C1875) provides a feed to the trailer pick-up (C1382) for the LH tail lamp and the number plate lamps on a B wire.

Stop Lamps
When the brake pedal is pressed, the brake pedal switch (C0075) provides a feed to fuse 3T of the trailer fuse box (C1875) on a GP wire. Fuse 3T (C1875) provides a feed to the trailer pick-up (C1382) for the stop lamps on an R wire.

Reverse Lamps
When reverse gear is selected, the CJB energises the reverse lamp relay. The energised relay provides a feed to fuse 6P, which is also located in the CJB. Fuse 6P (C0585) provides a feed to the trailer pick-up (C1381) for the reverse lamps on a GN then YN wire.

Fog Lamps
When the rear fog lamps are selected, the lighting control switch provides a feed to fuse 44P of the CJB. Fuse 44P (C0585) is connected to fuse 4T of the trailer fuse box (C1875) by an RY wire. Fuse 4T (C1875) provides a feed to the trailer pick-up (C1382) for the fog lamps on a U wire.

Turn Signal Indicator Lamps
When a LH indicator request is made via the LH column multi-function switch, the CJB provides a signal feed to the LH trailer FET. The LH trailer FET (C0585) provides a feed to the trailer socket (C1382) for the LH turn signal indicator lamp on a Y wire.

When a RH indicator request is made via the LH column multi-function switch, the CJB provides a signal feed to the RH trailer FET. The RH trailer FET (C0585) provides a feed to the trailer socket (C1382) for the RH turn signal indicator lamp on a G wire.

13 Pin Europe

Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 11E and fusible link 18E (C0632) on an R wire. Both are located in the Battery Junction Box (BJB). Fusible link 18E (C0570) provides a constant battery feed to the Central Junction Box (CJB) and fuse 8P (C0583) on an NS wire.

Fuse 8P (C0585) is connected to the fuses 2T and 3T within the trailer fuse box (C1875) by a GN then P wire. Fuse 2T (C1875) provides a constant battery feed to the trailer socket relay (C2937) on a U wire. Fuse 3T (C1875) provides a constant battery feed to the trailer pick-up (C0499) on a UK wire.

Fusible link 11E (C0570) is connected to the ignition switch (C0028) by an N wire. When the ignition switch is in the ignition position, current flows across the switch (C0028) to fuse 22P of the CJB (C0582) on a Y wire. Fuse 22P (C0585) provides an ignition feed to the trailer socket relay coil (C2937) on an R wire.

Trailer Socket Relay
The trailer socket relay coil (C2937) is provided an ignition feed by fuse 22P of the CJB (C0585) on an R wire. The relay coil (C2937) is provided a ground path on a B wire. The energised relay (C2937) provides a feed to the trailer pick-up (C0499) on an O then RW wire.

Tail and Number Plate Lamps
When the lighting control switch is turned to the side lamp position, the energised side lamp relay provides a feed to fuse 14P, which is also located in the CJB. Fuse 14P (C0583) is connected to fuse 5T and fuse 6T of the trailer fuse box (C1875) by an N then RO wire. Fuse 5T (C1875) provides a feed to the trailer pick-up (C0499) for the RH tail lamp on an N wire. Fuse 6T (C1875) provides a feed to the trailer pick-up (C0499) for the LH tail lamp and the number plate lamps on a B wire.

Stop Lamps
When the brake pedal is pressed, the brake pedal switch (C0075) provides a feed to fuse 1T of the trailer fuse box (C1875) on a GP wire. Fuse 1T (C1875) provides a feed to the trailer pick-up (C0499) for the stop lamps on an R wire.

Reverse Lamps
When reverse gear is selected, the CJB energises the reverse lamp relay. The energised relay provides a feed to fuse 6P, which is also located in the CJB. Fuse 6P (C0585) provides a feed to the trailer pick-up (C0499) for the reverse lamps on a GN then YN wire.

Fog Lamps
When the rear fog lamps are selected, the lighting control switch provides a feed to fuse 44P of the CJB. Fuse 44P (C0585) is connected to fuse 4T of the trailer fuse box (C1875) by an RY wire. Fuse 4T (C1875) provides a feed to the trailer pick-up (C0499) for the fog lamps on a U wire.

Turn Signal Indicator Lamps
When a LH indicator request is made via the LH column multi-function switch, the CJB provides a signal feed to the LH trailer FET. The LH trailer FET (C0585) provides a feed to the trailer socket (C0499) for the LH turn signal indicator lamp on a Y wire.

When a RH indicator request is made via the LH column multi-function switch, the CJB provides a signal feed to the RH trailer FET. The RH trailer FET (C0585) provides a feed to the trailer socket (C0499) for the RH turn signal indicator lamp on a G wire.

North American Vehicles

Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 6E, fusible link 11E, and fusible link 18E (C0632) on an R wire. All are located in the Battery Junction Box (BJB). Fusible link 6E (C0570) provides a constant battery feed to the trailer brake module (C2590) on a KW wire.

Fusible link 18E (C0570) provides a constant battery feed to the Central Junction Box (CJB) and fuse 8P (C0583) on an NS wire. Fuse 8P (C0585) is connected to the trailer socket relay (C2937) by a GN wire.

Fusible link 11E (C0570) is connected to the ignition switch (C0028) by an N wire. When the ignition switch is in the ignition position, current flows across the switch (C0028) to fuse 22P of the CJB (C0582) on a Y wire. Fuse 22P (C0585) provides an ignition feed to the trailer socket relay (C2937) on an R wire.

Trailer Socket Relay
The trailer socket relay coil (C2937) is provided an ignition feed by fuse 22P of the CJB (C0585) on an R wire. The relay coil (C2937) is provided a ground path on a B wire. The energised relay (C2937) provides an ignition feed to the trailer pick-up (C2586) on an O wire.

Tail Lamps
When the lighting control switch is turned to the side lamp position, the energised side lamp relay provides a feed to fuse 14P, which is also located in the CJB. Fuse 14P (C0583) is connected to the trailer pick-up (C0499 on 4 pin trailer sockets, C2586 on 7 pin trailer sockets) for the tail lamps by an N then NW wire. Fuse 14P (C0583) also provides a feed to the trailer brake module (C2590) on an N wire.

Stop Lamps
When the brake pedal is pressed, the brake pedal switch (C0075) provides a feed to the brake module (C2590) for the stop lamps on a GP wire.

Reverse Lamps - 7 Pin Socket Only
When reverse gear is selected, the CJB energises the reverse lamp relay. The energised relay provides a feed to fuse 6P, which is also located in the CJB. Fuse 6P (C0585) provides a feed to the trailer pick-up (C2586) for the reverse lamps on a GN then BG wire.

Turn Signal Indicator Lamps
When a LH indicator request is made via the LH column multi-function switch, the CJB provides a signal feed to the LH trailer FET. The LH trailer FET (C0585) provides a feed to the trailer socket (C0499 on 4 pin trailer sockets, C2586 on 7 pin trailer sockets) for the LH turn signal indicator lamp on a Y wire.

When a RH indicator request is made via the LH column multi-function switch, the CJB provides a signal feed to the RH trailer FET. The RH trailer FET (C0585) provides a feed to the trailer socket (C0499 on 4 pin trailer sockets, C2586 on 7 pin trailer sockets) for the RH turn signal indicator lamp on a G wire.