also, did some more looking with a flashlight into the enclosure cavity
last night... there is no "air button" to control the pump, so it can't
be connected to that. I'm still searching online, but so far most of
my searching brings up hottub dealers with very little technical info,
especially for bathtubs. If nobody has any ideas here, does anyone
maybe know of a more appropriate NG I can crosspost this to?

Thanks again,
Lou