Actually when re-reading my reply and your most recent post I thought of another question that is very important. When you had the 12 volt batteries in there, were there 4 of them and were they wired exactly as the 6 volt ones were? If that is the case you had a system voltage of 24 volts and you may have done quite a bit of damage to your inverter and to the control system.
Here is how the 6 volt batteries SHOULD be wired for series-parallel connection resulting in 12 volts at the inverter and 450 AH of capacity -- look on page 6 of the information here:
http://www.rvforum.net/miscfiles/batterycon-1.pdf
Hopefully you did not use this same connection pattern with the 12 volt batteries you had in there recently as that would result in 24 volts and possible damage. Let us know what you can about the situation at your coach...
Chuck