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.