The FL warning is letting you know the spa is not getting enough water to the heater.  This sometimes can result from having dirty filters.  If you know you have water passing through the heater some times the pressure switch, that is the little threaded switch in the heater with couple of wires coming off of it, may need to be adjusted to be less sensitive.  In some cases though the switch is bad and needs to be replaced.

Last updated on February 25, 2010 by webmaster