There is a Verified "Low Flow" (LF) Condition in the Heater.
The "HFL", "HL", or "HTR FLOW LOW" Fault has occurred 5 times in the Last 24 Hours or Less, and Heating has been Disabled. There is Not Enough Water Flow through the Heater to carry the Heat Away from the Heating Element. After the Problem has been Resolved, you Must Press Any Button to Reset and Restart Heater Start Up. Check for Water Level, Flow Restrictions, Closed Valves, Air Bubbles, and Pump Prime, or contact your Dealer or Service Organization.
Check for All of the following Conditions:
1. Low Water Level.
2. Blocked Suction Fitting.
3. Blocked Skimmer.
4. Dirty Filter.
5. Too Many Closed Jets.
6. Closed Slice Valve.
7. Heat Related Pump Not Running.
8. Heat Related Pump Not Primed.
For all Diagnostic Messages, click on below link.