Probably the easiest way to test if the 12s socket has been fully connected (many are fitted but only partialy used) is to check for power at pin4, this is the centre bottom (6 o'clock) pin on your 12s socket. Connect a meter or bulb from this pin to earth.
1):- Lights up without engine running - permanent live feed, reliant on caravan fitted smart relay or manual switch.
2):- Only lights when engine running - Split charge relay fitted and working.
3):- Doesn't light - not connected or not working
If "2" above shows relay to be fitted try looking around the
battery area, it will be an "add on" I'm 99% sure it won't have been an original fitment. Most likely their will be an obviously added wire connected to the
battery positive (+) terminal, follow this for a probable location.
Word of advice, even if system is already fitted don't assume that it is suitable, all too often the wiring and connectors are inadequate and usualy the reason for poor performance and chargeing of leisure batteries. At the Scottish meet I sorted a little problem for Lenny and couldn't believe how thin the wiring used was, and this looked to be the original fitted when the motorhome was biult.
You also may find this useful, standard wiring for 12S socket and cable colours. Clockwise when viewed from front.
Pin1 top (12 o'clock) female:- Reversing light or brake cutoff system. Yellow.
Pin2 (2 o'clock) male.:- Spare. Blue.
Pin3 (4 o'clock) female:- Earth. White.
Pin4 (6 o'clock) female:- Powerfeed for auxiiaries or split charge. Green.
Pin5 (8 o'clock) male:- Warning light. Brown.
Pin6 (10 o'clock) female:- Fridge. Red.
Pin7 (centre) female:- Spare. Black.
Although this is the current recognised set up sometimes "variations" are found, I also think their may have been an earlier version when 2 feeds were used, one permanent (pin4?) and the other switched/relayed (pin2?). Not certain on last point but may be worth doing above test on pin2 (and pin7) as well.
