Thirteen Pin to Seven Pin Adaptor in a Standard Duty Specification

Towing electrics: for towing a 7 pin trailer from a 13 pin socket, which is most people most of the time.

Towing is the one thing you can buy for a car where the wrong part is not merely disappointing. Every towbar listing here states the type approval number, the D value, the maximum noseweight and whether the bumper has to be cut, because those four facts decide whether a bar is legal on your vehicle and whether it will pull what you want to pull. Every electrical listing says plainly whether it is a dedicated loom or a universal one with a bypass relay, and what each will and will not do. We would rather lose a sale to a cheaper part than sell you one that does not fit.

Specification

• Fits: almost any 12 volt vehicle, which is the point of a universal loom
• Approval: ISO 11446 for 13 pin and ISO 1724 for 7 pin. Pin functions are printed on the instructions, because a socket wired to the wrong standard is the commonest cause of a trailer with no indicators on one side
• Rating: rated for a full trailer lighting load plus a caravan's fridge and charge feeds on the 13 pin versions
• D value: not applicable, this is an accessory rather than a load bearing towing part
• Noseweight: not applicable
• Ball height: not applicable
• Electrics: A universal loom with a bypass relay takes the trailer lighting power from the battery and uses the vehicle's light circuits only as a signal. It is cheaper, it fits almost anything, and it works. What it does not do is switch off the parking sensors, arm a stability programme, or tell the car that a trailer is attached. On an older vehicle it is the sensible choice. On a recent one with sensors and a tow mode, it throws away features you have already paid for.
• Fitting time: one to two hours on a dedicated loom, two to three on a universal one, because the universal has to be spliced and the dedicated plugs in
• Bumper: not applicable
• Materials: the standard specification, which covers the great majority of cars and caravans on UK roads
• Weight: approximately 0.25 kilograms
• Guarantee: three years
• Pin functions: printed on a card in the box and stamped on the socket, so nobody has to guess
• Coding: not required, which is the universal loom's one real advantage
• Parking sensors: will keep beeping at the trailer, because a universal loom cannot tell the car anything
• Testing: test under load, not with a test lamp. We sell a load tester on this page and it is the best sixty eight pounds a self fitter can spend
• Fridge and charge: pins 9, 10 and 11 on a 13 pin socket, live only with the engine running on any installation we supply

What arrives

• the loom or relay
• the socket where one is included
• cable ties, grommets and a gland
• a pin function card
• printed instructions

Fitting

One to three hours depending on which type. A dedicated loom plugs in and then needs coding on most vehicles, which we include free with any loom we fit. A universal loom needs splicing into the rear lamp circuits, and the splices are what fail in year four, so use proper crimps and heat shrink rather than the blue scotchlocks that come in cheap kits.

Before you order

A dedicated loom plugs into connectors the vehicle already has. It talks to the car's electronics, so the rear parking sensors switch off when a trailer is plugged in, the trailer stability programme arms itself if the vehicle has one, the bulb failure warning understands the extra lamps, and on many cars the fog lamp is muted as the regulations require. It costs more and on most cars it needs coding with a diagnostic tool, which we include on any kit we fit. A universal loom with a bypass relay takes the trailer lighting power from the battery and uses the vehicle's light circuits only as a signal. It is cheaper, it fits almost anything, and it works. What it does not do is switch off the parking sensors, arm a stability programme, or tell the car that a trailer is attached. On an older vehicle it is the sensible choice. On a recent one with sensors and a tow mode, it throws away features you have already paid for. In short: if your car has parking sensors, a tow mode, or bulb failure warnings, buy dedicated. If it is older than about 2010 and has none of those, buy universal and spend the difference on a load tester.