Refilled and started hot tub after 8 months empty. FLO error appeared on display. Only able to move temp in cooler direction - no increase in temp settings. Jets work with button pressed. Feels like circulating pump (just replaced) is working. Water feels cool - no increase in temp. Please advise on what to check next.
The FLO error could be caused by a clogged or dirty <a>spa filter</a>. You can try removing the filter to see if that makes a difference. A filter may look clean but can still clog if it has not been replaced with a new one in a while. You said that the spa circulation pump (http://www.hottubworks.com/SpaParts/PumpsCirculation.php) feels likes its working, you should be able to feel a small constant stream of water coming out of the heater return fitting. The other component that can cause a FLO error would be the flow switch (http://www.hottubworks.com/SpaParts/HeaterFlowSwitches.php). The spa will not heat in a FLO condition. When you push the button on the panel to increase the temperature does the display change settings and the spa if just not heating? Or does it reach a certain setting and will not go any further but you can then lower it?