Display shows HL or HLo and spa stops heating, sometimes with pumps still running

Safety first: Turn off power at the GFCI breaker before working in the equipment bay.

HL indicates the high-limit sensor has detected an unsafe temperature at the heater, often because water flow is too low.

• Inspect and clean filter: Remove the American Whirlpool filter cartridge and rinse thoroughly. Try running the spa briefly without the filter to see if the HL code clears (do not operate long-term without a filter).
• Check water level and suction fittings: Make sure the water level is correct and that no suction covers or skimmer openings are blocked by debris.
• Verify valves: Confirm all valves around the circulation pump and heater are fully open and that no check valve is stuck closed.
• Check circulation pump operation: With power restored, listen and feel for the circulation pump running. Weak or no flow at the heater return indicates a failing circ pump or blocked impeller.
• Inspect heater unions: With power off again, remove heater unions and look for scale, debris, or collapsed gaskets restricting flow inside the heater tube.
• Reset and test: Reassemble, restore power, and reset the spa. If HL returns quickly, the circulation pump or heater assembly may need replacement.

Persistent HL faults after basic flow checks should be diagnosed by a spa technician, as running with poor flow can damage the heater and plumbing.