12S WIRING & CHANGES 1998 TO 1999
The main differences between 1998 and 1999, are the 12S cable sizes, which were increased to reduce voltage drop and improve load capacity. Also, pin allocation changes have caused the car charge line (blue cable) to become redundant. In the new arragement the green cable charges the caravan battery when the engine is running: this then reverts to providing a power supply from the car battery when the engine is stationary. It is achieved by using a relay fitted to the caravan. To reduce the loading on the system the fridge negative was separated but unfortunately this caused problems with compatibility with the 12S sockets fitted to older cars.
OLD CAR with a NEW VAN
The old car will have split charge relay. The blue cable will not be connected in the caravan so the fuse in the line is redundant.
The fridge will not function because the black cable is not connected to the negative
Solution:
No action needed.
A separate cable (black) from pin 7 should be connected to the earth of the car; this should only be done in the car, not in the caravan!
NEW CAR with an OLD VAN
There will be no blue cable from the car to charge the battery, whilst the engine is running.
All the supplementary negative current will travel through the white cable.
Solution:
Either fit a split charge relay to the car, thus providing a blue cable to charge the battery or the fitting of relay inside the caravan to perform the same function as the one fitted to 1999 caravans, i.e. charge the battery from the green cable.
There is nothing we can do about this unless we replace the 12S lead and run a separate cable to the fridge from the new 12S lead.
Note:* For 1999 and later vans pins 3 & 7 should be independently wired to an earth point on the car.* Failure to observe this may cause overheating.
