This is a matter of personal choice and circumstance. There are three types of electrical kits and four types of connectors commonly available in the UK.
You would usually have the connector fitted that matches that of the connector on the caravan, trailer or light board. The type of electric kit will depend on your budget, which company is fitting it and availability. Not every kit is available with each connector, some may be available from one supplier but not the other, and you may have to shop around for different specifications.
It is possible that there will be a universal, after-market dedicated, or original equipment dedicated unit that will be available to fit to your vehicle. Which kit you decide to have fitted will depend on several circumstances.
As the title suggests, these kits will be suitable for most vehicle types, but are non-specific and require prior vehicle knowledge or research to fit them. There are two types: a basic kit, that draws power from the vehicle's own lighting circuit and a bypass kit, which utilises a dedicated power supply and uses the vehicle's lighting circuits as signals to switch relays.
Fitting a universal type of kit is the cheapest and can sometimes be the quickest method but has limited functionality and user benefits. However, this type may not be suitable for certain vehicles, especially those with sophisticated electrical systems; professional advice prior to installation is recommended.
These kits are vehicle specific, and have all the user benefits of the original equipment kit, but without the cost premium. However, availability can sometimes be an issue especially with new vehicle models. They are usually 30-50% cheaper than original equipment kits, but can take longer to fit than the cheaper universal kit. A dedicated kit is designed to be fitted to a specific vehicle and will not invalidate the vehicle warranty in any way.
Reliability and user assurance are the key features of original equipment kits. The kit is usually designed with the car at point of manufacture and installation will come under their warranty. The big disadvantage is cost and it may only be available when ordered with a towbar, which may only be one type. In addition, some functionality may be lost, especially with the 12S caravan supply, as the pin functions may not conform to conventional UK requirements and the kit or installer may not facilitate any alteration. A recent test, carried out by Witter Towbars, of over 80 vehicles with towbars supplied and fitted at the main dealer, found that 93% of original equipment electric kits did not have full UK specification 12S function.
This is the most common and cost effective type of connector currently used in the UK. It will fulfil all Normal towing requirements under UK law and can be used with lighting boards, cycle carriers, caravans, garden trailers, plant trailers and horseboxes. In fact, almost anything you can connect to a towbar.
This consists of a Normal connector as above and a similar extra Supplementary connector that can supply a caravan, horse box or tipper trailer with a switched and permanent twelve volt power supply, extra earth connections and a reverse light facility. A 12S socket is only required if you wish to charge the battery and power the fridge when travelling. Having both connectors on the towbar can be bulky and unsightly especially when fitted to a detachable towbar.
This is a single connector of similar size to that of a 12N connector but it contains both 12N and 12S functions in one. It is a waterproof connection with a unique twist lock system for safe and reliable contact.
The socket is smart and discreet, ideal for towbars with a swing away socket plate. The cost is higher than having separate 12N/12S connectors. However, as all UK caravans manufactured after 2008 will have a 13-pin connector as standard this will soon become a popular choice.
This is a clever socket that looks like a 12N socket and is compatible with a standard 12N plug, as found on garden trailers and lighting boards. It may also be used as a 12N/12S connector when used with a WeSt plug on your caravan which has standard the 12N configuration and 6 extra pins that supply the 12S function.
THE WeSt SOCKET MUST NOT BE USED WITH METAL TRAILER PLUGS.
7 pin is cheaper and widely available but bulky and can be unreliable. 13 pin is more costly and can be difficult to source but is reliable, secure and future proof. WeSt 13-pin is rare but very convenient and cost effective. All caravans manufactured in the UK after 2008 and all trailers and accessories manufactured after 2010 have ISO 13-pin connector as standard.