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Intermittent trailer lighting

Symptom: Trailer lighting flashes.

Intermittent trailer lighting

Background

When using a trailer with a 7-pin connector connected according to one of the following alternatives


• all exterior lighting is connected to either pin 5 or 7 in the 7-pin connector

• extra power consumers (e.g. heating fan) are connected via the trailer's connections for lighting (pin 5 or 7 in the 7-pin connector)


the load becomes too high in the car's REC and in the electronic module for the trailer. This results in the electronics switching on and off which means that the trailer lighting is intermittent.

Fault symptom

Trailer lighting flashes.



Procedure

Alternative 1 (recommended)

Replace the trailer's connector and wiring harness with the 13-pin version. Extra power consumers are then connected to pin 9 or pin 10.

Important

If connected to pin 9, the car's battery could be drained if the trailer is connected to the car and the car is not driven.


Pin No.
Function
Max. load
1 Direction indicators L 6 A (short term)
2 Rear fog lights 30 A
3 Ground
4 Direction indicators R 6 A (short term)
5 Exterior light R 6 A (max. nominal load 50 W)
6 Brake lights 30 A (short term)
7 Exterior light L 6 A (max. nominal load 50 W)
8 Reversing lights 25 A
9 +30 (constant power supply, max. current 20 A) 20 A
10 +54 (power supply via car's ignition switch, max. current 30 A) 30 A
11 Ground for pin no. 10
12 Not used
13 Ground for pin no. 9


Alternative 2

Make an adapter harness with a 7-pin female contact for connection to the trailer's connector at one end and a 13-pin male contact for connection to the car's connector at the other end. The connectors are connected together as follows:

Important

A rear fog lamp (if fitted) cannot be used on the trailer. If connected to pin 9, the car's battery could be drained if the trailer is connected to the car and the car is not driven.


7-pin female contact, pin no.
13-pin male contact, pin no.
1 (Direction indicators L) 1
2 (Extra power consumers) 9 (constant power supply, max. current 20 A) or 10 (power supplied via car's ignition switch, max. current 30 A)
3 (Ground) 3
4 (Direction indicators R) 4
5 (Exterior light R) 5
6 (Brake lights) 6
7 (Exterior light L) 7