Towbars & Towbar Electrics

Tow Bar Wiring – Why its so important
Throughout their lifetime, a number of products and technologies have undergone change and development.
Take the modern computer for example. From it’s original design, so big as to fit into any standard living room to now,the literal size of a notebook. The first innovative Video recorder, which was state of the art some 20 years ago, has developed into a hand-held device incorporating a disc of plastic to play and record.

All such products have changed and developed but in essence, still perform the purpose they were intended.
The same approach has been made within the modern motor car. With the onset of network technologies being deployed in the vehicle of today, any accessory equipment installed into such vehicles has also to mirror the technology.

The UK’s towing industry had for many years, remained static in the way they applied and installed towing electrical equipment.

Much of this was down to the lack understanding of vehicle technology and the implication of this in respect to the function of the towbar. In some cases, it was an unwillingness by towbar specialist’s to attempt to understand and change their practices.
Even as a vehicle owner, very little knowledge of operating systems was passed on by manufacturerer’s and this meant towing electrics had became just another accessory and therefore, of little importance.
No emphasis has been given to the technology improvements in the way a vehicle tows a trailer and this lack of knowledge and appreciation has sadly meant a continued use of towing electrical systems which were only applicable 8 -10 years ago.
With the advances in technology requiring a higher specification for towing electrics also meant a different price structure, and it is this variance in price which has been allowed to dominate the choice made by the car owner who only sought to find the cheapest provider without considering or understanding the technology in the car.
This lack of appreciation by vehicle owners and installers alike, naturally leads to such technically advanced systems being By-Passed with the use of universal towing electrics.
Where once the nominal By-Pass relay avoided bulb failure check systems, their application now has the effect in seriously compromising specific systems within vehicles and this can lead to disastrous consequences.

We are glad to say that great leaps forward have been made within some areas of the towing industry over the last few years, mostly through the marketing of information by Right Connections UK Limited, who we are agents for here in the Channel Islands and a wider availability of products. However, there still remains a lack of understanding and acceptance throughout the majority of trade and public alike. As consumers and owners of vehicles, it is extremely important that you try to understand that towing equipment has become singularly the MOST IMPORTANT accessory to be installed on to a motor vehicle and as such, must be given it;s rightful place, particularly in value, as an essential contributor to vehicle safety.

Not only would the implications of failure to the actual metal construction of the towing device be devastating, but almost more importantly is the behaviour and performance of the vehicle when it is towing! There are a number of vehicle systems which need to be aware that a towbar has been installed and this notification is made through the electrical connections and some of the vehicle networks have to be altered diagnostically. There is no other accessory which has this sort of architectural change.

In the following pages, we will explore some of the reasons why it is important to consider the fitting of a vehicle specific wiring kit.


What is wrong with using Scotchlok Connectors ?

The official description for this part are: Insulation displacement connectors

In the late 1970’s, the US based 3M company designed a simple connection to join 2 wires together. This connector was primarily designed for the telecommunications industry and not the automotive! The common brand name for this was called a Scotchlock. It is not known why this name was chosen but it has come synonymous with this type of connector. They have always been received with mixed reviews and have even been banned by at least one country for maintaining repairs! In the late 1970’s and early 1980’s, wiring used in motor vehicles was principally fairly heavy gauge and was developed with what would be considered as a substantial PVC insulation. In addition to this, all the signals that the wiring transferred were a basic 12vDC . This technically meant that any current was a 12v signal on or off. The displacement connection was meant to be a temporary fix and connecting a spur onto such relative heavy wire using this connector, was not really such an issue for short term repair solutions. What ultimately happened was that these connections developed into a permanent fix and naturally, over the years that followed, a growing number of problems developed.

During the late 1980’s and 1990’s, vehicle wiring harness development became much more streamlined and lighter, thinner insulated cabling became the standard. The now widely accepted displacement connector started to prove to be inadequate and this was addressed purely by producing a connector with a thinner cross section cutting joint! In the meantime, vehicle manufacturers were developing more than just 12V on/off signaling on these harnesses and it is fairly conclusive that the use of such connectors can have a detrimental affect on the process of such signals!
Below, is a list of issues which effect the use of such connectors:
* There is no physical way in telling if the connection has been made correctly.
* Creates damage and interference on the vehicle harness
* Cannot use these in a non waterproof environment
* Vibration has a weakening effect on the joint.
* The splice is not precise enough and can cut the copper cores
* Splice wire can easily be pulled out from the connector

What about Soldering..
Isn’t this a better option? Soldering has been seen as a justifiable alternative to the use of the displacement connector. One of the major problems with soldering is that joints made using this process fail to be sufficient. In order to make a fully insulated, gas tight and effective joint, will mean that some form of heat shrink or similar tubing be applied over the finished joint. To enable this tubing to be installed will require the cutting of the main harness wire in order to slide over the tubing. The ends of the cut wire are then bared, along with the taped wire and all 3 laid together, tinned with flux where necessary, and soldered together. The insulated tubing is then slipped over the joint and heat applied to shrink the tubing over the joint. Some heat shrink tubing also has an adhesive which secures fully the tubing to the wire. What actually happens with most installers is that they cannot be bothered to actually cut the main wire, so they either use a sharp knife and cut away some insulation or use the soldering iron to melt the insulation to expose the copper core. They then solder the spur wire to this small section and cover the whole thing in PVC insulation tape. The end result is a badly formed solder joint which is not gas tight insulated. This joint is also prone to vibration and heat variance which can often make the insulation tape become unstuck. Accepting that the Scotchlok connection is not suitable for wet environments, some feel soldering is the viable alternative. Unfortunately, unless such joints are made correctly, wrongly made joints can also lead to major connections problems.

Here are some of the reasons not to select a solder joint application:
* Joint has to be made exactly to the correct criteria
* Joints are not gas tight (can be if heat shrink is used) and as such can become a source of ignition
* Permanent damage to harnesses.
* Cannot easily remove the installation without further damage to the vehicle harness!
* Some vehicle manufacturers DO NOT PERMIT solder joints to be used for repair!


I have been offered a 7 way By-Pass system in my car, is there anything wrong with these?

The installation of a by-pass relay is exactly that. The original idea of the by-pass relay was introduced in the early 1980’s and was a means of making connections onto lighting circuits of motor vehicles, that either had a special bulb checking system or if the vehicle’s electrical system was not capable of supporting any extra load imposed by the lighting on a trailer for example. In such vehicles, the option of the by-pass was a very good solution. They work by detecting the signal produced when a light is switched on. This signal activates a relay in the unit and through the connection of the by-pass unit to a permanent 12v power supply, switched the power from the car harness to actually driving the trailer lights through the fixed 12v live supply. Such relays were a good solution for a number of years, but problems and issues then started as vehicle technology increased.
Vehicle control modules were able to control vehicle lighting and as such started to send pulse and signals through the lighting harnesses and the by-pass relays could not handle such changes. Over time, many variable formats of the by-pass relay were produced to tackle the advances in technology.
In addition to this, vehicle’s are now operating on bus networks, vehicle safety systems rapidly developed and more effective protection was afforded. This also meant manufacturers would develop braking systems that could detect the presence of a trailer and would therefore control the uncontrolled snaking of a caravan for instance.
The problem is with such developments, the installation of a By-pass relay meant that the vehicle would not detect the trailer and therefore such safety systems were rendered ineffective! The other feature worthy of note is the use of screw terminal blocks which are commonly found on most manufactured By-pass relays. These are mounted onto the relay circuit board. They are designed to accept the 7 core universal cable which is mounted to the towing socket. There are a number of problems with this form of connection as they are prone to vehicle vibration and as with any screw terminal fixing, the action of screwing down bare copper has the effect of breaking the strands or spreading the core wires and not forming the correct contact. A number of German vehicle producers do not accept this type of design on OEM electrical parts that would be installed into their vehicles.

Over the last 7 or 8 years, we have seen huge changes with the introduction of vehicle network systems. This has only been possible with the broad use of CAN bus. The subsequent changes in this development has required that the trailer electrics be visible to the car. The persistent use of By-pass relays WILL NOT permit the trailer to be detected by the towing vehicle and as stated earlier, many vehicle safety systems have become compromised by the continued use of by-pass technology.

What do the vehicle manufacturer’s say?

As the owner of a such a networked vehicle, you should be aware that your choice of a by-passed electrical installation will adversely affect vehicle safety systems and may also be contrary to the requirements of your vehicle manufacturer! This continued practice has since caused a number of issues with certain vehicle manufacturers and in the case of the Audi/VW group for example, they make their customers aware of certain issues in regard to the choice of towing electrics.

This information is commonly found in the vehicle owner’s handbook.

Here are 2 extracts from a VW Tiguan as an example:

Page 46 -Booklet 3.2 Driving; Never connect the trailer’s electrical system directly with the electrical connections of the rear lights or to any other unsuited electricity supplies …

Page 54 -Booklet 3.2 Driving; The trailer stabilisation system can be activated by your Volkswagen partner if a towing bracket is retrofitted, provided compatible electronic components are fitted …

Fitting a By-Pass relay will be contrary to both of these requirements! Also within the wider manufacturing process of vehicle wiring harnesses, the actual wire sizes and core components have changed. Small wire sizes have been the most notable change which entailed a thinner insulation. All of these changes have been effectual in reducing the weight of the harnesses used thus contributing to energy saving through reduced fuel usage and emissions. For those manufacturers who have no objection for connections that are made on the lighting harness, have stipulated that any connections made have to be made with the use of specific vehicle connectors and not through the use of displacement connectors or soldering which ultimately damages the harness!

Why choose specific towing electrics ?

Specific electrical wiring kits are designed entirely around the requirements of each individual vehicle. If the vehicle technology is such that signals for trailer lighting can be taken from the lighting circuit, then wiring kits are produced to use the original connectors as found fitted to the vehicle rear light assemblies or any alternative central connector. This naturally entails a wide and varied design of towing electrical harnesses. If the vehicle technology requires the wiring installation be integrated into the vehicle network, then again, a specific wiring kit will do exactly that.
For these latter technologies, it will mean that the towing electrics are now seen and monitored by the vehicle and the vehicle will understand what is required when towing a caravan or trailer.
This is exactly as the manufacturer has intended.

Many thousands of Pounds, Dollars and Euros have gone into researching the effects on the vehicle when towing and as vehicle safety is paramount for practically all manufacturers, the behaviour and correct control of the towed caravan / trailer is equally important in contributing to a safer road environment. Where a manufacturer does not permit connections through the rear lighting harness will naturally mean some other connection is required. This is usually made through the 2 wires of the vehicle’s comfort CANbus and a special towing module is installed which actually becomes integrated into the vehicle network thus enabling communication to the presence of a trailer. Using Original Connectors.. The beauty of using original connectors actually means the towing electrics will become part of the architecture of the vehicle rather than a tacky add-on feature. There are approximately, 15-20 different manufacturers of connectors used in the automotive industry and that is a lot of connectors.
Here is a list of the advantages in using original connectors:

1 / The electrical contact is absolute as this is produced through male and female terminals within the connector.

2 / Less than 0.01% failure in the connection.

3 / Connectors are joined together and locked in place

4 / If connections are made on the outside, the use of special sealed connectors ensures against water ingress

5 / No damage to vehicle harnesses

6 / Easily installed and removed (if necessary)

7 / Designed to become part of the original harness architecture

In addition to the use of original connectors, a specific towing kit will also be equipped with a safely designed trailer module relevant to the vehicle. This is added into the towing harness again, using a specific connection system and NOT with the use of screw terminals or wire connectors. This again, ensures against contact issues caused through vibration etc. Specific towing kits for CANbus vehicles. For these vehicles, a specific wiring kit is a must. A growing number of vehicle manufacturers have and are integrating their operating systems through the use of a CANbus network.
If you draw a parallel with a car and a home computer, it is the same principal. When you push the ON button on your computer the computer boots up. This principally means the PC looks for all the installed devices such as a CD drive, Keyboard, Monitor etc and after a short while, is in a ready for use status.
Likewise, with a motor vehicle it is the same. When the key is turned and ignition is on, the car activates all the installed control units until the vehicle is in a ready to go position. Motor vehicle networks have to naturally operate on a far quicker speed rate than a home Pc. With a specific towing kit, the trailer module is part of this boot up process. Without this, or if a 7 way by-pass has been fitted, then the car will not detect the presence of a trailer module and can not activate or de-activate relevant systems.

A growing number of manufacturers (e.g. Ford, Land Rover, Mercedes,Volvo) have installed prepared connectors which have the relevant signal bus transfer wires fitted. A specific towing kit will mate with this preparation. A vehicle manufacturer surely would not invest in this installation just to have the system by-passed! Such preparations are now part of an ever widening network within the modern motor vehicle industry and the trailer connection is no exception. Below is a list of some of the systems that require changes to how they operate with a trailer connected: (NOTE: this varies from manufacturer to manufacturer and are in no particular order)

1 / Braking System
2 / Cooling System
3 / Gearbox Suspension
4 / Adaptive Cruise Control
5 / Blind Spot Alert Systems
6 / Instrument Cluster
7 / Parking Aid
8 / Self-Park Systems Parking Brake
9 / Lighting System (Rear Fog lamp)
10 / Vehicle Alarm System

What about the cost?

This is always a major consideration when inquiring about the price of a towbar fitting. Most vehicle owners have a pre-conceived idea as to the cost of having a towbar installed. What is evident is that this view does not take into account the technology deployed in the vehicle and the manufacturer’s requirements. Therefore, most vehicle owners expect to pay the same figure as they did some years previous when they last had a towbar fitted. Add to this, the vehicle owner that only has the use of the Vehicle for a year say, and as a result, would generally look to take the cheapest solution. Neither of the above cases takes into consideration what is best for the vehicle and so contribute to the manufacturer’s aim in supplying a vehicle that not only is more economic but in towing with a higher degree of safety for all concerned. Naturally, choosing a specific towing kit will in most cases, mean a higher cost than a universal solution. As we have tried to point out, each towing kit is tailored to be suitable for the particular vehicle and the costs in design and development vary from vehicle to vehicle. They are far more than a piece of 7 core cable and a towing socket!
However, if you choose a specific towing kit from Hudson Motor Company, then you are guaranteed to know that, through Right Connections Ltd, we lead the field in our knowledge and expertise in providing the first choice in towing electrics.

Dramatic Changes in the law.

This section potentially has the greatest influence on the future of towing electrics. Unknown to the average towing customer, and we would include the majority of the towbar aftermarket, that significant changes are currently being made to the law throughout all the member states of Europe. Here we find the most significant changes to what can be and what cannot be installed into motor vehicles. In 2007, a draft document was drawn up in Europe, to detail the whole approval process to virtually all motor vehicles and their trailers.

This document is known as: DIRECTIVE 2007/46/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 5 September 2007 Establishing a framework for the approval of motor vehicles and their trailers, and of systems, components and separate technical units intended for such vehicles. The details that this document covers are very wide and contained within this document are details contained in paragraph 14 that refer to components and systems installed that have a counter effect upon vehicle safety.

Such statements have become significant and there are currently a number of committees set up to actually discuss and evaluate the situation regarding towing electrics. This document is now being discussed in Europe and over the next 2 years, will become ratified within the EU states. Such changes in the law will radically alter the current perception that towing equipment is just another cheap accessory!

In Conclusion

We trust that the information contained herein has given you more of an insight as to why a specific electrical wiring installation is singularly the most acceptable method of connection. They should always be your first choice.

Call 01534 878847 for further information or email