Do you need a reason to take care of your trailer socket? It's very simple. To prepare yourself, get used to always disconnect the trailer first and then disconnect the power cable. At some point you forget the latter and since the plug is additionally secured by the cover or twist lock and the cable is attached several times up to the rear lights of the trailer, simply pull it out of the plug housing (joke).

Then they can't even drive to a garage, because of course neither turn signals nor brake lights work. Good advice for do-it-yourselfers is needed there. This service is actually already available in this Chapter in the form of a pin assignment. Start what? With the ground, of course, which all functions need. If you have the e.g. by the color brown and opening at least one trailer- rear light, you don't even need a multimeter.

So a little attention or better caution should be exercised. Why, if you can find out all functions by trial and error? So, activate the brake light on the towing vehicle, the must then also burn on the trailer. Likewise turn signals and then ...

At this point a warning is issued. With older systems, the trailer may be directly protected by fuses of the towing vehicle. In the event of a possible short circuit, you have two defective vehicles. Searching without an allocation plan for the fuses can be very time-consuming. Also only two very special ones can be responsible for the two sides of the complete lighting system, which are difficult to procure.

A stop is recommended here, because there are two sides for the parking rear light and you can only switch them on together. So it would be possible that you could interchange them on the way towards the trailer. If you have a short circuit there at some point, even a trained eye will look for the error a long time, because the error is always suspected on one side only.

The last connection 54g is then left and can be wired accordingly. It is free because it had a function that is no longer needed today. Is more than one additional connection necessary or the trailer or towing vehicle are newer, a thirteen-pole connection may be available. If this is different with both, then intermediate pieces help, which of course exclude additional functions.

Examples would be the rear fog lights or reversing lights on the trailer or a 12V power supply on the caravan. By the way, the former still hold a small complexity. Whoever connects a trailer and checks very precisely, should also check the function of the rear fog light. No, not only on the trailer, also on the towing vehicle. Its rear fog light must be switch off by a mechanism in the socket to avoid unpleasant reflections.

The installation of a modern wiring harness when installing a trailer coupling is only recommended if the vehicle manufacturer has prepared it to the extent that of the luggage compartment and only plug connections have to be clipped in (see video).