Hot Springs Hot Tub not so Hot

I have an old (1999) Hot Spring tub that won't heat. We turn the temp down during the week to 85, then turn up on Friday to enjoy the weekend use. It has been turned down since the first week of Feb, too cold to use it. This past Thursday I turned it up to 104 like usual. Friday afternoon I went to check chems for Friday night fun, and it was cold. For some strange reason, the tub won't show the temp, but has ready light when its up to temp.
Friday afternoon I opened the control...

Hot Springs Hot Tub not so Hot