Kevin,
Regarding your ‘bird circuit board’ eight-pin connector.
Pin #4, orange wire, goes to the battery boost switch on the dash.
Pin #5, purple wire, goes to the battery disconnect switch on the dash (‘salesman switch’).
Both dash switches are normally hot and complete their respective circuits using the switch backlighting ground.
I took readings at the eight-pin connector on our coach.
Big Boy de-energized;
Pin #4: domestic battery voltage
Pin #5: ~11.5-volts
Big Boy energized;
Pin #4: ~4.8-volts
Pin #5: ~11.5-volts
I wouldn’t think that your BIRD/Big Boy is contributing to your issue. If the Big Boy was remaining closed after disconnecting from shore power your chassis batteries would also be depleted. The BIRD/Big Boy would not affect the house battery charging from the inverter/charger.
I agree that by disconnecting the inverter/chargers at the positive post on the invertor you have essentially eliminated them as the draw down on your domestic (house) batteries.
Both the Front and Rear Run Boxes feed various circuits from the domestic batteries. All high amperage circuits enter the rear run box via the large terminals along the bottom of the box and then feed through high amperage circuit breakers to their destination.
The Front Run Box is fed from the Rear Run Box by two separate circuits, one is constant hot (not affected by the domestic battery disconnect switch), and one is switched (domestic disconnect switch). These feeds are exposed in the front run box so you could use your clamp-on meter two measure amp draw on each feed. You could also totally eliminate the front run box from the equation by disconnecting the two large terminals at the front wall of the Front Run Box.
2008-2009 Indexed Beaver and Patriot Wiring Diagrams in the Coach Assist section.
Drawing # 38070173 on page 155 shows the feeds to the Front Run Box.
Eliminating the Rear Run Box from the equation would be tough. Many of the components in the rear run box are buss-mounted which makes reading amp draw difficult, however most of the high draw circuits do utilize cabling that would allow you to use your clamp-on meter.
Drawing # 38080547 on page 175 of the same diagram set shows the various Rear Run Box components labeled by source (Domestic v Chassis).
Be aware and use caution as some circuits in both the Front and Rear Run Boxes are still hot with high-amp 12-volt power even with the battery disconnect switches off.
A couple of other diagrams that might be of interest:
DC diagram for the dual invertor
Page 22
Drawing #: 38010651
AC diagram for the dual invertor
Page 32
Drawing #: 38030071
All of the diagrams that I listed are in my 2006 Patriot hard copy wiring diagram and are effectively the same as the 2008-2009 diagrams, some of the 2008-2009 diagrams are ‘colorized’ and a little easier to read.