Thank you everyone for the help on this.
To close the loop on this thread, I replaced the Link10 with a Xantrex LinkLITE Battery Monitor.
I would have preferred to replace the unit with the Victron BMV-700 Battery Monitor as I think the specs looked better and in my opinion Victron is a more reputable company and the unit was cheaper. I think Xantrex and Mastervolt are one and the same. However, the Victron required new cabling to be run.
The Xantrex fits in the same hole as the Link10, uses the same wiring and wiring configuration, the same size fuses and also uses the same shunt rated at: 500A 50mV
It is much easier to program than the Link10 (but then again programming a Mars rover would be easier than setting up a Link10).
So far, so good. I am now getting negative values when I turn off the battery charger and positive values when I have the charger on; A very good sign. All indications are the Link10 main unit failed.
With best regards,
Super Maramu 2000
Currently cruising: St Augustine, FL