Spa does not heat; temperature remains far below setpoint even though pumps run

Safety: Turn OFF power at the GFCI breaker before testing heater circuits.

• Check for error codes: Look for FLO, OH, dr, or other codes that would prevent the heater from energizing. Resolve those first.
• Verify heating mode and setpoint: Ensure the spa is in Standard mode and the set temperature is above the current water temperature.
• Measure heater voltage: With power ON and a call for heat active (and only if you are qualified), measure voltage across the heater terminals on the control board. You should see full line voltage (e.g., 240V). If there is no voltage, the board or safety circuits are not allowing heat.
• Test heater resistance: With power OFF and heater disconnected, measure resistance across the heater element. A typical 5.5kW/240V element reads around 10–12 ohms. An open circuit indicates a failed heater.
• Replace heater if open: Remove the heater tube assembly from the plumbing, install a Bullfrog-compatible replacement heater with new gaskets, and reconnect wiring.

If the heater tests good but never receives voltage with proper flow and no errors, the control board heater relay may be defective and the control pack may need replacement.