Gary,
With the echo charger flashing green, there is no connection from the chassis batteries to the house batteries so bad chassis batteries aren't affecting you house units.
Since you need 13V from the house battery bank to get the echo charger working, check the voltage across the complete house battery bank, not across a single battery. Place 1 probe on a house battery post on the inner-most batteries (posts closest the center of the coach. This will probably be a negative (-) post. Place the other probe on a post closest to you and the outside of the coach. This will normally be a positive (+) post. With the meter set to DC volts and a range of 20V or greater, you should be reading approximately 12 to 12.5V based on yuo 6.1v measurement mentioned earlier.
With the inverter charger on and the coach plugged in to shore power or teh generator running, this voltage should go to 13-14 volts, as Gerald noted earlier.
Steve