I'm getting the FLO error. It flashes with the temp. I've removed the filters, open the drain until water comes out, but the only thing that will get the FLO message to go away is to turn the pumps on HIGH. But now ever so often you can hear the pumps RPM drop slightly and then regain speed. The problem is that the heater will only heat the water with pumps on high but they don't seem to stay on for more than 20 minutes. So I have to keep going outside and turning them on again to get the water at 102 degrees. This is a pain since its 15 degrees outside. Is my pressure switch going bad? Its only 4 years old. Can the switch be bad even if the wires pass the continuity test?

HELP!

I am having the same problem with my thermo spa. Did you figure what the problem/cause was with yours? I replaced the pressure swith, all the T's are fully opened. I even went as far as to replace the circuit board and still get the same thing. I hope someonecan help.