electrical conundrum

[griff71]

hi again. afraid this will probably be long winded.
i'm in the process of fitting a B2B charger, i will also be wiring my compressor fridge direct to battery. these wires and relays were under the rear passenger seats, one set runs to the hab battery so that will be the old split charger (which doesn't have power. another one goes to the diesel heater, (which has no power) and then 2 run to the front, 1 to the battery and one to a switch which i presume is for the heater.
on the board from top left to right it has written in pen the following:-
Charger
Battery
Switch
Stat Out
Off
On
Stat in
so my question is this, will it be ok to rip out all of that wiring and install my b2b and the fridge straight to battery, also i was going to run another cable from battery to a fuse box which i will install under the seat to power some usb chargers i plan to fit by the dining area and also for a new diesel heater if that old one is dead.
hope someone can advise on the above as i don't want to rip it all out only to find i've stuffed other things up.

 

[berni109]

Think most of us would like to see a wiring diagram and the results of a multimeter test on the voltage states before offering advice.

 

[griff71]

all voltage is 0, with the whole lot, fuses are fine but i've gone through the whole board with a multimeter with engine running and without engine running, also with EHU. I'll try and do a diagram when i get home from work. thanks