Final update. Got the new motor/battery box. Installation was simple and we are back in the PB CG business. Good thing too. My wife said she has forgotten how to use the regular vaccum hose setup.

I have disassembled the other box to try and troubleshoot. It appears that it is the motor, not the switch, wiring or battery that has gone bad. Quite a bit of rust at the front end of the motor, probably the seal was leaking - though we never noticed any water in the motor compartment. I am going to be in touch with Watertech again to try and get parts so I can try and fix the down box, if I can get it running I'll save it for the future.