Display shows HTR ERR or Htr, heater does not turn on even though pumps run and temperature is below set point.

Safety first: Turn off power at the GFCI breaker and verify with a meter that power is off before touching heater wiring.

• Inspect heater terminals: Remove the equipment bay panel and check the heater terminals on the control pack for burned or loose connections.
• Check continuity: Disconnect heater leads and measure resistance across the heater element with a multimeter. Typical values are in the 8–20 ohm range depending on wattage. Infinite resistance indicates an open element.
• Inspect for thermal fuses: Some heater assemblies include a manual reset or one-time thermal fuse. Check for a small red reset button or inline fuse and reset/replace as needed.
• Replace heater: If the element is open or the housing is leaking, replace the complete Arctic Spas heater assembly.
• Board issues: If the heater tests good but never receives power when there is a call for heat, the heater relay or control board is likely faulty and should be replaced.