1980 Itasca Spectrum DC Recent Power issue in Coach

[hankey01]

Hi everyone,

I'm experiencing some electrical issues with my 1980 Itasca Spectrum motorhome and would really appreciate some advice.

Problem Description:

    Everything worked fine on AC power during our recent camping trip, including the water pump and fridge.
    The fridge seemed to work fine on DC power while driving to the campsite.
    However, on the way back, after switching the fridge from AC to DC, the water pump and interior lights stopped working.
    When I got home and plugged the motorhome back into AC, the lights and water pump worked again.
    I checked the fuses in the living area and they seem fine.
    The coach battery has been dead for over a year, but everything was functioning (presumably off the engine battery) until I disconnected the AC power.

Additional Context:

    Under the hood, there are two batteries: one for the engine and one for the living area. The living area battery is completely dead.
    Given the context of my current situation (going through a divorce and financial constraints with kids almost reaching adulthood), I'm hoping to find a cheap and easy fix as I can't invest a lot of money into it right now.

Any suggestions on what might be causing the issue and how to resolve it would be greatly appreciated.

Thank you in advance for your help!

[RockwoodMike]

If you have a set of jumper cables, try jumping power from the good engine battery to the dead living area battery..See if things come back on in 12 volts for the lights and fridge..

Maybe there is some relay that needs 12 volts from the living area battery to make the switch over from AC to DC..

Jumping the batteries may make the relay do it's thing

[hankey01]

That's a good idea..will try it. 

Thanks!