The modern motor vehicle has evolved greatly over the years but over the last few years the changes are much more dramatic with the advancement in technology of the vehicles electrical and safety features.
Universal / Bypass System
Universal wiring kits have been used for many years it consists of a socket a length of 7 core wire and either a indicator warning buzzer or in most fittings now to modern vehicles a bypass relay. The bypass relay is fitted between the vehicles electrical lighting harness and the socket, the wires of the bypass have to be fitted directly to the vehicles lighting harness and a power supply added to power the bypass (this method is now being frowned upon by manufactures and in many cases using this method will invalidate the vehicles electrical warranty).
Vehicle Specific Wiring
In most cases a vehicle specific wiring kit is more expensive than a bypass system however there are major benefits to be gained by installing this type of kit. We know from talking to customers that people think the kits are plug and play and all vehicles have one plug in the boot to attach it to the vehicle, unfortunately that is not the case, in many fits wires have to be taken to the front of the vehicle and the connectors are behind panels requiring a lot of trim to be removed. Fitting the wiring can take from 1 - 4 hours.
If your vehicle has a manufactures warranty fitting a universal wiring kit could invalidate the electrical warrant because you have connected on to the vehicles wiring harness and not used the manufactures connectors . Manufactures warranties will specify that any tow bar wiring fitted must be equivalent to the wiring supplied by the vehicle manufacturer. Dedicated wiring kits are made to fit a specific car make and model. Vehicle specific kits are when fitted an extension of the vehicles main wiring harness in effect the trailer or caravan becomes part of the towing vehicle and the computer is aware of this and takes that into account when running system scans and makes adjustments were and when appropriate. It will automatically adjust the following systems if fitted :-
When the system activates, the driver really has to concentrate on steering the vehicle within as straight a line as possible. While he is engaged in this, the vehicle is automatically decelerating and braking individual wheels to control the ‘snake’ or ‘fishtailing’ as it is sometimes called. It is also possible that the vehicle will have to accelerate marginally to help control the snake. The driver has no control over the brakes or accelerator during this phase, but when the vehicle has been corrected, control will be passed back to the driver. This is indicated by the ESP lamp extinguishing in the instrument display.
If the car begins to skid, the driver will usually attempt to brake and hopefully try to drive into the direction of the skid. In practice, this does not always happen, so the car will try do it itself. If the system operates correctly, the vehicle will:· Respond by taking over the accelerator and operate this independently... · Apply pressure through the braking system regardless of how much pressure the driver applies... · Alter the steering angle (if the vehicle is equipped with electronic steering wheel control - e.g VW)During this time, it is usual to see the ESP lamp light and can be accompanied by a continuous ‘pinging’ noise. The duration that ESP operates is variable and dependent on how quickly the car comes back under control.
After a vehicle specific wiring kit is installed a compulsory software download is required on many vehicles to activate the towing systems, on some vehicles no trailer lights will work until a download is completed.