How to Fitting a towing socket

Fitting a towing socket

Here you can get Fitting a towing socket, Supplement and Towbar Electric Socket Types. A caravan or trailer must, by law, be fitted with certain warning lights. These are wired up to a standard plug socket called a 12N socket which provides a 12 volt supply to power the indicators, stop lights, tail-lights, number-plate illumination and fog lights.

While the 12N socket is adequate for operating the obligatory lights, you’ll want to run power from the car for other, non-essential accessories like reversing lights. A caravan without its own battery can also need extra power for interior lights, a refrigerator or a pump . For this you would like an additional towing socket.


The extra socket that’s fitted to the car to supply the power needed for these additional items is known as a supplementary or 12S socket. it’s fitted almost the first socket and, just like the original one, features a seven pin connection inside. you’ll identify the supplementary sockets by their grey or white caps.

The standard sockets have black caps.

If you’re fitting a tow bar, and you plan towing a caravan, it’s worth while fitting both types of socket. You can buy both ordinary 12N sockets and supplementary 12S ones within the sort of an entire kit from an adjunct shop or towing specialist. The kit should include all the things you would like to suit the socket to the car like mounting brackets, wiring, weatherseals, indicator relay , dash-mounted red light and securing screws.


If your caravan features a built-in battery you would like how of keeping it charged up. You can, of course, connect a mains charger if there’s a convenient supply, but an alternative choice is to suit a special combination relay that’s connected into the car’s charging circuit. this enables the car’s generator to charge the auxiliary battery.

Combination relay

12S Connections

The international code for the supplementary towing socket is: 1 (L) Yellow— reverse light 2 (54G) Blue—spare 3 (31) White— earth 4 (R) Green — accessories or battery 5 (58R) Brown —warning light 6 (54) Red — refrigerator only 7 (58L) Black— spare

2. Extra bracket

If you are fitting the 12S socket in addition to the 12N unit you will need to fit an extra mounting bracket. Refer to the instructions and fit the bracket under the tow ball unit. If you are fitting both types of socket mount the double bracket to the towbar.

3. Socket wiring

To wire up the 12N socket, see Projects 15. The 12S socket is wired in the same way. Strip back about 40mm of outer insulation from the cable and bare the seven wires back about 1/4in (6mm) each. Follow the code in step 1 and connect the wires to their respective terminals in the socket.

4. Attach socket

When the unit has been wired up, fit the weatherseal to the back of the socket, then fit the entire assembly to the mounting bracket. Align the screw holes in the socket with those in the bracket. Fit the securing bolts into the socket, fit and tighten the nuts at the back of the unit. Run the wire into the boot.

5. Wire up feed

The yellow wire, pin 1, connects to the car’s reversing light circuit. Blue and black wires, pins 2 and 7, are not used. The brown wire, pin 5, is used for a warning light supplied with some caravans for dangers such as lowered support legs and handbrakes. To wire the red and green wires, pins 4 and 6, see sideline.

6. Wire to earth

The earth wire is the white wire connected to pin 3. Run the wire to a suitable point on the body of the car. Fit a ring connector to the end of the wire and find an existing earth point or drill a hole and fix the wire with a self-tapping screw. Make sure the earth connection is tight.

Towbar Electric Socket Types

There are 3 types of towing electric socket.

Single 7 Pin Electrics

Single 7 Pin Electrics also referred to as 12(N), are fitted as standard with any towbar.

They provide power from the towbar to the lights on a trailer or caravan. If you’re only getting to be towing a trailer this is often all you would like. You can tow a caravan using only single electrics, but the inside functions of the caravan, like the fridge, wouldn’t have power to them. you’d need an adaptor if your caravan has 13 pin electrics. Even if you’ll only be using the towbar for a cycle carrier we recommend that you simply still have one socket fitted in order that you’ll power a light-weight board over the bikes.

Twin 7 Pin Electrics

Twin 7 Pin Electrics, also referred to as 12(S), are fitted in addidtion to single 7 pin electrics if you are going to use your towbar for towing a caravan built before 2008.

The extra grey socket provides power to work the inside functions of the caravan like the interior lights, run the fridge and charge the battery while you’re towing. This type of socket has been replaced on caravans built after 2008 within the UK. New caravans now use the 13 pin standard socket shown below.

13 Pin Electrics

13 Pin Electrics are standard in most other European countries for a few time.

This is replacing the two separate socket currently utilized in the uk. The 13 pin socket is actually the 2 7 pin sockets merged in to at least one. All caravans manufactured within the UK from 2008 are fitted with an ISO 13 pin connector as standard. this technique uses one socket with 13 pins inside, rather than the traditional two separate 7 pin sockets. 13 pin sockets also are used on some vehicles especially with detachable towbars when there’s not enough room to mount two separate sockets behind the bumper.


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