My spa is a 1999 Allure model from Vita Spa. I too had a pesky FLO message over the years that occurred randomly despite cleaning, replacing, and even removing the filter. I could live with the problem since it occurred too infrequent to cause real heating issues - until this season when it wouldn't go away. I finally solved the problem and would like to pass on what I learned.

I found my new persistent problem to be the pressure switch that's screwed into the top of the tubular heater. The old switch was locked and wouldn't pop up - under ANY amount of water pressure produced by the pumps.

Unfortunately the FLO message persisted after the installation of a new switch and wire. By new wire, I mean the one that connects the pressure switch to the circuit board. This wire has a phone jack on one end and two female blade connectors on the other. When you remove a 6 year old wire from the pressure switch, it basically disintigrates.

The new switch tested O.K. with a multi-tester, but the new wire did not have continuity from one end to the other despite appearing to be solidly attached. It turns out that the tiny (and I mean tiny) wires were not securely soldered -if at all- to the blade connectors. The heat shrinked tubing over the wire hid the flaw. I stripped the ends of the wires and soldered and crimped them securely. I also had to adjust the new pressure switch by turning the thumb wheel on it to ensure it engaged under pressure.

I believe the original intermittent FLO message was due to a poor connection in the wire that lets the circuit board "know" the pressure switch has been tripped.

Hope this helps.