Ok, so we bought this used and ended up replacing the circuit board & Upper Control Panel, got it hooked up to 115v and kept getting FL error. Replaced the pressure switch and after finding how to adjust the sensitivity, thought we were OK; No more FL message...until the pump shuts off, either auto or manually. When the pump is off, still get the FL error. All the jets are working, the filter is new so, what am I missing here? I've attached a picture of the circuit board and the heater with the old switch, so you'd know what configuration I have.
Anyone? Also, when the pump is running on low, even though the Heater light is on, the water is not coming out heated/warmer than what is in the tub. I tested this when the water was 95 an had the heater set to 100.
8/17- Thought I had the problem solved by re-adjusting the sensitivity on the pressure switch. Maintained 101 up to midnight, when I took the trash out, I heard the pump running on low and the heater light was on and held at 101. Got up the next morning, late and checked again; FL was displayed and the temp was at 100!
New circuit board P/N 51491, New Upper Control Panel, New Pressure Switch.
Old board jumper for 20A/50A was set to 50A; moved that to 20A, Filter jumpers B-A set to B.

Ok,so we had a tech come out and on the filter jumpers, he moved the jumper from B to A and it seemed to be working good. However, after a couple of hours, the temp had dropped 2 degrees and the Heater light was still lit. It was heating last week for a day so now we have to check on whether the heater needs replaced.
I shut off power to the system & checked across the two lines from the heater; closed circuit.
Turned the power back on & checked voltage across the two contacts; 115v...
Something is still wrong because the heater is not heating the water...???