Location of vehicle supply cable on Inca EK

Hello, Can anyone please help me with this problem. I have an indication of 0 volts from the vehicle battery on the remote panel. I have checked the conversion relay fuses under the bonnet and all showing voltage as expected. I then checked the supply to the Sargent unit in the wardrobe. Leisure battery cables (2) showed correct voltage. Vehicle cables (2) both showed zero volts. Everything else is working correctly. Does anyone know where the supply from the front end of the Inca comes from? It was all working okay until about a week ago. ie charger was charging vehicle battery on selection and leisure battery , also on selection. The colour code of the cables for the vehicle battery at the Sargent end are brown with dark green tracer and brown with blue tracer for leisure battery. Is the supply taken from one of the vehicle fuses possibly?
I would be very grateful of any thoughts or comments on this.