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Towbar electrics |
Tow bar electrical sockets. |
Cars which are fitted for towing caravans will also be
fitted with at least one, if not two electrical connection
sockets attached to or adjacent to the tow ball. Commonly
known as 12N and 12S sockets. Power from the vehicles indicators,
fog lights and sidelights is transferred to the caravan lights
of the same type through the 12N socket, whereas the supplemental
power required by the caravans reversing lights, battery
charger and fridge are sourced through the 12S socket. If
you are fitting your own 12S socket you need to remember
to fit a split charge relay to your car as well, this ensures
that power to these high drain devices on your caravan only
flows when the ignition is turned on. Should you not fit
a relay of this type to your car and take a break during
a long tow, you are likely to find that your car battery
will not have enough power to start the engine when you resume
your journey.
There are some important differences in the 12N and 12
S socket wiring in caravans manufactured up to 1998 and
after 1999. The 12N connection has larger cables to help
reduce voltage drop, however the pin allocation is identical
to that of 1998. The 12S cable sizes for 1999 models have
been increased to reduce voltage drop and improve load
capacity. The car charge line (blue cable) is now left
unused, the caravan battery is now charged via the green
cable whilst the car engine is running, when the car is
not running the green cable reverts to providing a power
supply from the car battery, this action is produced from
a relay fitted in the caravan. Also the fridge negative
has been separated to reduce the loading on the system
which unfortunately may cause compatibility issues with
some older cars. |
The 12N socket. |
The socket is coloured black and houses 7 pins which are
are numbered 1 to 7 and need to be connected using the correct
grade wiring as follows (1998 Pin Allocation).: |
1998 Pin Allocation |
|
Pin |
Cable Colour |
Function |
1. |
Yellow |
Left turn signal |
2. |
Blue |
Fog
light's |
3. |
White |
Earth |
4. |
Green |
Right turn signal |
5. |
Brown |
Right
hand side light |
6. |
Red |
Brake
lights |
7. |
Black |
Left
hand side light |
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The 12S socket |
The socket is coloured grey and houses 7 pins which are are
numbered 1 to 7 and need to be connected connected using the
correct grade wiring as follows : |
1998 Pin Allocation |
|
Pin |
Cable Colour |
Function |
1. |
Yellow |
Reversing light |
2. |
Blue |
Caravan Battery or charger |
3. |
White |
Earth |
4. |
Green |
Constant 12v feed |
5. |
Brown |
Sensing device |
6. |
Red |
Refrigerator |
7. |
Black | |
Spare |
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