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Trailer Socket buying guide — what to know before you buy

A trailer socket (towing socket) provides the electrical connection between the vehicle and a towed trailer, caravan, or bike carrier requiring rear lights. UK and European vehicles use 7-pin (N-type) or 13-pin (ISO 11446) sockets. The 7-pin socket provides basic lighting functions, while the 13-pin socket also supplies a 12V supply for interior caravan power, fridge circuits, and reverse light. Sockets corrode, crack, and suffer pin damage from repeated connection cycles. Replacement is a straightforward DIY job requiring basic wiring knowledge. At CarParts247 we stock 7-pin, 13-pin, and combined sockets with wiring looms for direct-fit applications.

7-pin vs 13-pin sockets

Choosing the correct socket type depends on what you will tow and the wiring already installed in your vehicle.

7-pin (N-type, BS ISO 1724): handles left/right indicators, brake lights, reverse, fog, and earth
13-pin (ISO 11446): includes all 7-pin functions plus 12V supply, battery charging, and rear interior lights
Most modern caravans use 13-pin connections — use an adaptor if vehicle has only 7-pin
Bike carriers, box trailers, and boat trailers generally only require 7-pin connections
Some vehicles allow fitting both sockets — check the wiring loom capacity

Wiring and installation tips

Incorrect wiring risks blown fuses, damage to the vehicle's ECU, and lighting failures when towing.

Use a relay or towbar bypass module on modern vehicles with multiplex wiring — never splice direct
Towbar-specific wiring kits are vehicle-keyed — use the correct kit for your make/model/year
Waterproof the socket housing with silicone grease on the pin contacts
Keep the socket cap fitted when not towing — exposed pins corrode quickly
Test all light functions with the trailer connected before every journey

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Frequently Asked Questions

What is the difference between a 7-pin and 13-pin trailer socket?

A 7-pin socket covers basic trailer lighting. A 13-pin socket adds a 12V power supply for caravan accessories and a charging circuit. Modern caravans use 13-pin connections.

Can I wire a trailer socket myself?

On older vehicles with a conventional wiring loom, a direct wiring socket kit is a reasonable DIY job. Modern vehicles with CANbus multiplexed electronics require a vehicle-specific bypass relay module to avoid ECU faults.

Why are my trailer lights not working?

Common causes include corroded socket pins, a blown trailer fuse, a failed bypass relay, or damage to the trailer's own wiring. Test the socket voltage with a meter and check the fuse box for a dedicated trailer fuse.

What size fuse does a trailer socket need?

Typically a 7.5A or 10A fuse protects the lighting circuit. The 12V power supply pin on a 13-pin socket is usually protected by a 15A or 20A fuse. Check your vehicle's handbook and wiring kit instructions.

How do I clean corroded trailer socket pins?

Use an electrical contact cleaner spray and a small brass brush to remove oxidation from the pins. Apply a thin coat of silicone grease or contact-protective grease afterwards and fit the socket cap when not in use.