Future use of pin 12 within the euro plug
As this currently seems to be a grey area I thought it would be a good idea to explain.
Terminal 12 within the euro plug if used, is the facility for a drawing vehicle to detect a caravan or trailer is connected, so the drawing vehicles ECU is able to make automatic adjustments to some of the following vehicle functions; bulb failure warning systems, stability control systems, switching out of drawing vehicles rear fog lights, vehicle alarm, engine management and possibly changing shift patterns of an automatic gearbox just to name a few.
This facility has been available to use for many years within the 12s auxiliary plug system but has been used very seldom by car manufactures in the past due to compatibility problems as countries in the past have not been able to agree on standardising the use of one particular pin terminal.
Just to give you one example; some continental countries used pin 2 for this facility while the UK used pin 2 for caravan leisure battery charging and pin 5 for this facility until the September 1998 wiring changes then they changed to pin 2 for this facility. so it was impractical to fully implement this system in past years, not to mention most cars in the past were not ECU controlled.
Now the euro plug is here this changes everything, we now have a European standardised pin to use for this function and as time passes during the next few years my prediction is that this facility is going to come into force in a big way as more and more vehicles are becoming controlled by ECU's.
This is basically how the system detects a caravan or trailer is connected to the drawing vehicle; a signal is sent through a wire from the vehicles ECU to pin 12 within the drawing vehicles euro socket. When a caravan or trailer is connected to the drawing vehicle within its own euro plug, pin 12 is bridged (linked) to pin 3 earth return wire, this in turn earth out the signal wire from the drawing vehicles ECU telling it that a caravan or trailer is connected so it is able to make the necessary adjustments.
If and when you may decide to upgrade your caravan to the 13 pin euro plug, it would be professional to bridge (link) pin 12 to pin 3 within your caravans euro plug while fitting the plug in advance of time for the above reasons.
I hope this information is of use to you and I wish you good luck in what ever you endeavour to do.
Kind regards
Snowy1