I think I have sussed a way to achieve this....
I intend to make a switch box that uses a double pole switch to enable the selection of :
A) Normal operation controlled by the Elecktroblok
B) Off / Defrost
C) Fridge runs off 12V from leisure batteries.
The box will have 3 cables converging
A) Takes the original EBL Plug on Block 1
B) Is inserted into the EBL socket on Block 1
C) A 12 v 20A fused feed from the aux batteries.
This will result in a plug and go module, using the existing EBL plugs and sockets that does not disturb the original installation and can be removed to restore the factory defaults.
The fridge switching is currently being done by the EBL-100, whose 12v is taken off the engine
battery/alternator.
These and the alternator D+ wire are fed into the EBL on Block 2.
This block will remain unchanged.
The EBL provides the switched supply out of EBL-Block 1, directly to the fridge :
BLK 2/Pin 1 - n/c
BLK 2/Pin 3 - D+ Alternator
BLK 2/Pin 4 - Positive 12v
BLK 2/Pin 5 - Negative 12v
When 12v is put on EBL Block 2 pin 2 (D+), this activates the fridge relay which switches in 12V from the Starter
battery.
The EBL then outputs the fridge 12v from Block 1.
This ensures that the Fridge can only be running on 12v when the alternator D+ activates the fridge relay.
So an overview of what I intend is to insert a 2 pole, 2 way, center off toggle switch, configured to allow selection of:
Normal/Defrost/12v permanent.
I'll house the switch in an enclosure and wire in a 4 way Plug on one cable, to go into the EBL Block 1 and a second cable with a socket that will take the original EBL Block 1 connector.
Feed a 12v fused supply to one side of the switch, taken off the aux batteries,rather than the starter
battery.
A) Switch position 1, will ignore the modification and operate as per factory.
B) Switch position 2, Defrost/off removes all voltages from the fridge supply and ignores the EBL normal function
C) Switch position 3, Diverts 12v from aux batteries and feeds fridge directly.
Looks sound to me, How efficiently the fridge will operate remains to be seen, but I will know soon enough, once the mod is installed and operational for a day or so.
I'll update as things progress.
james
