Over the years, also changed the installation of a tow bar in the vehicle, while in cars prior to 2000, you could mount a tow bar with a simple 7 or 13 wire harness - connect directly to the wires of the rear lighting of the vehicle (position, stop, turn signals, fog lights) and the car was operational and fit to drive, when installing a tow bar in a modern car must be remembered to install the module relieving the installation.

There are, of course, occasionally modern cars in which it is enough to connect a simple STANDARD 7 or 13 PIN harness, but with the development of on-board electronics these are really cars counted in the promille.

We recommend that the harness and the hook be installed in a specialized workshop. When properly choosing an electronic harness with module for a given vehicle, we need to know basic information about the car, these few sentences will help us choose the right harness with module.

Basic information:

• most important: what will be plugged into the vehicle (cargo trailer, platform for example, bicycle, camping trailer)
• Model and year of the car
• whether the car has parking sensors

Let us explain what the purchase of a 7 PIN or 13 PIN harness depends on.

The simplest explanation is to decide what you want to use the towbar for.

7 PIN harnesses are mostly used for lightweight trailers.

Lightweight trailer - according to Polish regulations: A trailer with a maximum permissible gross weight not exceeding 750 kg. The actual weight of the trailer must not exceed the weight of the towing vehicle. To drive a vehicle combination with a lightweight trailer entitles you to category B, C1, C, D1, D. That is popular cargo trailers that can be rented in any rental company. The trailer has a simple set of lights: position, stop, indicators x2, weight, power, fog lights. Mostly it is small and maneuverable enough to not have a fog light.

The 13 PIN harness has an extended harness with reverse light support, used on all kinds of:

• two-axle trailers
• towbars mounted platforms (bicycles, extra racks)
• Caravans - this harness is much more extended with additional functions such as powering the trailer while driving (fridge).

The three most important types of harnesses used in vehicles:

STANDARD harnesses consisting of a wiring harness ending in a 7 or 13 pin socket, a set of quick connectors and the screws and ties needed for installation.

UNIVERSAL harness with module - functionally extended harnesses, necessary during installation in most vehicles of German manufacturers produced after 2000, initially the cars had only CHECK CONTROL function consisting of control of burnt out bulbs and showing the icon on the dashboard. The next step was the introduction of a digital CAN-Bus protocol - the module also performs a number of other functions, but about this in the following section on functionality. The modules are based on relays (U1L) or the more advanced ones on processors (U2P, U3P).

DEDICATED harnesses with the module - original harnesses offered by car manufacturers, they are characterized by easy assembly but the price of the harness is a deterrent + in many cases the assembly at the car dealer is necessary (it is necessary to change parameters in the car computer).