I have a thermo spa park avenue deluxe model 2001 series. Hot tub worked great last winter. we drained it this summer and just filled it 2 weeks ago. We get the flo error flashing along with the temperature. The heat only works if the jets are on full speed. I have the filters out, have replaced pressure switch, water level is great and even replaced the circuit board. Any idea what to try next? Please help, someone must have the same problem.