1994 Dimension 1 "Colisieum", Flo 1 popped up in early May 07, at which time we drained and cleaned tub. Upon refilling it this past week and after assuming the Flo 1 issue was solved by replacing the diaphrams on the Ozone "Air Pump", we turned it on, got both jet pumps primed and running and the Flo 1 comes on. Last night we pulled the filters out to see if that cleared up the issue but it did not. We did notice that when the Jet 1 is running the heater will work, but once the jet stops the heater stops.
Any suggestions? It's getting to be perfect hot tub weather here and we're stuck out in the cold watching a flashing flo 1 switch.
Should we replace the whole air pump?

It sounds as though the pressure switch is remaining closed (detecting pressure) when the jet pump is off. Since the system should not be pressurized at that point, it gives you the error (It thinks maybe the pump is running when it shouldn't be).

This is why it will run fine until it reaches temp, then you get the error.

Replace the pressure switch.

Thanks for your response. We will check the pressure switch. However, the heater only runs as long as the Jet 1 pump is running (the std. 30 minutes) when the jet pump kicks off, the heater does too.