Blinking FLO on read out. Water still circulates, but no heat. Reset works for a moment, then back to FLO. Checked the connection leading to the filter, but it seems to be clear. Any suggestions?

Check the power reaching your controls, you may be only getting 120 instead of the needed 240 for heat.

Blinking FLO on read out. Water still circulates, but no heat. Reset works for a moment, then back to FLO. Checked the conection leading to the filter, but it seems to be clear. Any suggestions?

If there are shut off valves in the connections, make sure they are all the way open. (pulled up for slide valves)
Sensing it has a water FLO problem and will not engage heat.

1. Old filter restricting water flow, try running without filter in.
2. flow/pressure switch has deposit build up, needs recalibrated, or going bad

3. Pump getting week, on its way out possibly, not pushing recommended amount of water.

Slim possibility of an air lock if it was just drained and refilled.