Tesla Issue!

[Hutch]

so what does the without brakes figure refer to?

That refers to a trailer without brakes, the type that you would use for taking rubbish to a tip.

 

[IanB1485]

It is an interesting conundrum , the Permanent 12V normally activates a relay(s) to cut off the caravans 12V systems , excluding the fridge control supply. The normal test is that when connecting up the car to the caravans' electrics the caravans awning light won't come on once the car is hitched. A second pin on the 13 pin connector has 12V on it when the cars ignition is on , The permanent 12V is then connected (by the fridges' control system) to run the fridges' 12V heater element ( 125- 150W) which the cars alternator can supply, no problem.
The difficulty is if you want the caravans leisure battery to supply the ATC electronics , which doesn't take a lot of current you must ensure the 'ignition On' pin hasn't got 12V on it otherwise the fridge may, if on automatic select 12V operation and this would flatten the caravans battery within a couple of hours which would also stop the ATC from functioning. as the battery flattens.On my PHEV the fitter took a fused supply cable direct from the battery (which is below the boot of the car) to the permanent 12V pin on the 13 pin connector. the unfortunate thing is he couldn't tap into the Cars CAN system to detect when the engine is running so the 'Ignition ON' pin has also got 12V on it all the time, which means when stationary and systems off ( service stations , ferrys e.t.c) I have to unplug the caravan to stop the cars 12V battery going flat trying to run the fridge.