First off, welcome to winnieowners!
Second, you should add a signature to your user profile. It usually includes the year, make and model of your coach, but can include other information. A signature is appended to each post. To create/edit a signature, click on the "User CP" link in the orange bar at the top, then click on "Edit Signature."
Follow this path to see how the 12V feeds get to the monitor panel:
Winnebago Manuals and Diagrams
Wiring Diagrams - Motorized
2003 Wiring Diagrams
Typical (39QD): Holding Tank Monitor Panel
Typical (39QD): Body, 12 Volt Wiring Diagram
(sheet 2, zone A-34)
House batteries to monitor panel:
Circuit JA from house circuit breaker panel below refrigerator (sheet 2, zone A-4)
Chassis batteries to monitor panel:
Circuit ER from chassis wiring connector (sheet 2, zone D-13)
Typical (39QD): Automotive Wiring Diagram
(sheet 1, zone B-32)
Circuit ER from chassis circuit breaker panel (sheet 1, zone B-23)
Guide to circuit abbreviations (a.k.a., Secret Decoder Ring): Wiring Identification Guide
Operator manual for 2003 Journey DL
(pages 2-16 and 2-21) says the house battery disconnect switch is located on the dash, and is labeled "AUX BATT." This switch must be on to power the house circuit breaker panel. Of course, the solenoid that the AUX BATT switch controls must also work correctly, to pass house battery 12V to the panel.
The switch that is used for connecting the house and chassis batteries is also on the dash, but is labeled "AUX START."
Various diagrams show the house and chassis battery connections, including the AUX BATT and AUX START solenoids. I leave finding and tracing those circuits (on the diagrams) to you. The solenoids themselves are in the chassis electrical box (ref. page 9-8 of the operator manual).