Almost embarrasing. At first thought was switch as had power going to it but motor not running, so replaced switch & motor still not running. So, either replacement switch no good (used), or bad motor. So (with old unit) figured out which of the 4 prongs on motor elect. connector are + & -, & rigged up "jump start" wires from batt. to attach & see if would run. Lo-n-behold, discovered that the elect. connector to motor had unsnapped, only a fraction & not really visible but worked fine after re-snapped it. Lou had explained how component works & to test elect. portions. I am really relieved, now have a clean bowl & fluid, & enjoying black beauty again.