Control indicates 'Inlet Sensor Error', 'Return Sensor Fault', or similar; water temperature control may be unstable.

Safety first: Turn off power. Allow piping to cool if necessary.

• Locate inlet/return sensor: Identify the sensor on the cold water inlet or return line to the water heater or indirect tank coil.
• Inspect and reseat connections: Disconnect and reconnect the sensor plug at both ends to wipe oxidation from contacts. Look for corrosion or moisture intrusion.
• Check cable routing: Ensure the sensor cable is not routed alongside high-voltage wires or tightly wrapped around pumps, which can induce noise or damage insulation.
• Test sensor resistance: Using a multimeter, measure resistance and compare to the manufacturer’s chart. Replace the sensor if readings are inconsistent with actual pipe temperature.
• Replace sensor if needed: Install a new Weil-McLain compatible inlet sensor and secure it firmly to the pipe or well.