Apart from spare bulbs, split pins, wheel bearings and fuses, it’s wise to take an extra electrical plug with you on holiday, since these plugs do break.

If you’re lucky, it’s only the cover, but sometimes, you need to replace the whole thing. The slit is at 4 , while 1 is always at the top. The contact points at the back of the plug are also numbered this way. 

Unfortunately, not all 7-wire cables are the same. The colours might differ.  Here is a general guideline.

1 - yellow for left indicator

2 - blue for power to fridge or to charge battery from vehicle

3 - white (sometimes pink) for earth

4 - green (sometimes purple) for right taillight

5 - brown for taillights (in older caravans, the taillight on the right*)

6 - red (or orange) for brakes

7 - black for taillights

* In older caravans 4 and 7 are usually bridged and 7 is then used for the other taillight.