Retrofitting a towbar with a wiring kit - manual

Not all cars have a factory hitch, either because this was not considered when ordering the car or the original owner did not require one. Now you're thinking about retrofitting your hitch. But what to look for? This manual provides an overview of trailer towing technology and conditions.

Tow bar installation requirements

Hook - a practical thing . However, technology has advanced a lot with trailer hitches as well. Over the past few years, on-board wiring has taken a qualitative leap, and the legal requirements for driving a car with a trailer have become more stringent.

This article covers the following topics related to retrofitting a towbar with a wiring kit:

1. Driving license for towing a trailer in traffic jams 2. Various trailer hitch options 3. Additional specifications for the wiring kit 4. Installing a towbar with a do-it-yourself wiring kit

1. The right to tow a trailer: what is valid in our country

A full category B driver's license allows you to drive a car or van with a maximum authorized weight of up to 3500 kg, towing a trailer with a maximum authorized mass of up to 750 kg if you passed your driving test on or after January 1, 1997 . Alternatively, you are allowed to tow trailer with MAM over 750 kg , if the common MAM of trailer and tractor does not exceed 3500 kg .

If you want to tow heavier trains, be sure to follow the steps on the Home Office website for towing a trailer. You can apply for a temporary license for a medium sized truck and trailer. After passing the truck test, you can take the driving test for obtaining a driving license category C1+E . Before purchasing and installing a trailer hitch, check your driver's license for the trailer you wish to tow and apply for the necessary license if necessary.

Keep in mind that a general full driving license is enough to transport bicycles.

2. Various towbar options

The critical value for trailer couplings is the maximum permissible load, i.e. the load on the trailer coupling. And trailers and cars have an acceptable load.

The maximum allowable load on the car , as a rule, is indicated in the vehicle registration certificate provided that the car was equipped with a tow bar by the manufacturer .

2.1 Compliance with the permissible load of the car and the towbar

There are exceptions: several luxury models, racing cars and hybrid cars (electric motor combined with internal combustion engine) .

• If the registration documents indicate the maximum allowable load , it is necessary to distinguish between drawbars with or without CE marking.
• If the towbar is CE marked , you just need to keep the documents for the towbar at hand.
• Store documents in the glove compartment . For vehicles and towbars without a documented permissible load, contact the MOT or DEKRA service center.

The specialist can insist on installing a reinforced suspension on the rear axle . To determine this, the road train is checked by measuring the distance between the trailer hitch and the ground.

She should be in within 350 - 420 mm . In addition, additional loading of the tractor must be provided. The permissible load is deducted from the maximum permissible additional load.

2.2 Special towbars for bicycle trailers

There is another difference between the available trailer hitches .

• Some trailer hitches are not designed for a real trailer, but for bicycle transportation .
• In the case of trailer hitch without CE mark you can get a record of using a bike trailer on your registration papers.
• Manufacturers offer cheap couplers for trailers, especially suitable for bicycle trailers.

3. Technical versions of the towbar

For technical versions of towbars, there are:

- rigid tow hook
- detachable tow hook
- swivel tow hook

3.1 Rigid towbars

Rigid tow hooks are usually the cheapest and have a higher load capacity. . The difference between very cheap and more expensive rigid trailer hitches is often impossible to discern at first glance.Difference in price depends on the quality of the steel alloy used, but especially on corrosion protection. In this regard, different manufacturers make different choices.

3.2 Removable towbars

Removable tow hooks have become more common. They let you take your head off making the towbar almost invisible .

Depending on the type of construction Part of the tow hook may be visible under the bumper. Removable tow hooks mounted vertically or horizontally .

• Vertical detachable drawbar the devices are usually hidden behind the bumper.
• Other are inserted into the square profile under the bumper and secured.

Tip for detachable tow hooks: not everyone chooses to permanently remove the tow hitch . With few exceptions, the law does not require the tow hook to be removed when not in use.

Nevertheless , this is a legal gray area as there have been no legal precedents so far. Leaving the trailer hitch in place greatly increases the risk of an accident and the extent of possible damage. Collision with another vehicle while reversing, or alternatively if the vehicle collides with the rear of your vehicle, the trailer tow hitch can cause significant additional damage .

3.3 Rotary towbars

Swivel tow hooks simply swing down and out of sight. This system is relatively new. So far, he has not been able to prove himself.

3.4 Additional specifications for wiring kits

The type of wiring kit depends on the vehicle . The difference is between older models with traditional wiring and cars with digital systems.

The latter has CAN bus system , i.e. two-wire cable that controls all functions. Most of the differences arise between CAN bus systems , depending on the make or model of the vehicle.

Cars with CAN are usually equipped with towing wiring . Some vehicles require the control unit to be turned on after connecting the trailer control module and its cables. This can only be done by an authorized workshop of the manufacturer. It may be necessary to integrate the control to deactivate the parking aid.

In old cars with simple wiring, when adding a wiring kit, the flashing signal relay and trailer warning lamp must also be retrofitted. Often, wiring is included with these elements.

3.5 Choosing the right socket: 7-pin or 13-pin

Moreover , you can order identical wiring kits with 7-pin or 13-pin connector . Additional connections are important for certain trailers such as caravans. In addition to wiring, they can be equipped with a constant positive and charging current ( e.g. when installing rechargeable batteries ).

Only very simple trailers are suitable for the 7-pin plug without any additional features .

Since the requirements may change and the price difference is negligible, we generally recommend a wiring kit with a 13 pin socket . Using an adapter, a 13-pin car socket can be connected to a 7-pin trailer plug.

4. Installation of the towbar

4.1 Installation of wiring

A visit to a professional garage can be beneficial, especially for the wiring kit. For the CAN bus in particular, faulty connections can lead to severe and costly damage. Otherwise simple 7-pin connectors usually connected to the rear light wiring ( turn signal, brake light, tail light, rear fog light and reversing light ).

The installation kit should contain an extensive installation manual with a detailed electrical diagram.

4.2 Installing the towbar

Installation instructions are included with every high quality trailer hitch .

However, the installation is simple.
– A car lift or repair pit is recommended. When using jacks, the car must be fixed with axle stands.

Now the installation is very easy.
– Towbars are made under the car. The connection points are arranged in such a way that the corresponding drilling holes are already in place.

– They are located on the base frame or bottom reinforcements.

– For off-road vehicles and off-road vehicles with a ladder frame, the trailer hitch is simply inserted between the ladder frame and screwed tight.

– All other vehicles already have drilling holes, as these vehicles can also be ordered with a tow bar.