No Power to Dash/Chassis

OK, here is what has apparently happened. My coach has a battery isolator solenoid. That solenoid should charge both house and chassis sets of batteries when either set require it. The coach has been plugged in all winter to the in-house float charging system. For ten years, that has kept both sets charged while the coach has not been in use. I replaced all my batteries a little over a year ago. The chassis batteries were almost completely discharged, even while the coach has been plugged in. I highly suspect that the battery isolator unit has gone bad. It no longer charges both sets of batteries, house and chassis, only the house batteries. So now, if recharging the chassis batteries does not work, I will not only have to replace the isolotor solenoid, but also two year-old chassis batteries. Here is the unit I just ordered. https://pdxrvwholesale.com/products/battery-boost-solenoid-1500-amps-intermittent-duty Thanks for the help. Hopefully this will remedy the problem.