Heater display shows erratic or rapidly changing water temperature readings.

Safety: Turn off power before handling sensor wiring.

• Inspect sensor connectors: Reseat inlet and outlet temperature sensor plugs on the control board and at the sensors.
• Check wiring routing: Ensure sensor wires are not bundled tightly with high-voltage or pump motor wires that can induce noise.
• Test sensors: Measure resistance of each sensor and compare to Pentair’s chart. Replace any sensor with unstable or out-of-range readings.
• Improve water mixing: If sensors are installed in plumbing where hot and cold streams mix poorly, consult a professional about relocating or adding mixing length.