Boiler shows 'Supply Sensor Fault', 'Supply Temp Open/Short', or supply temperature reading is unrealistic.

Safety first: Turn off power and allow the boiler to cool before touching piping or sensors.

• 1. Locate sensor: Find the supply temperature sensor on the outlet piping or in a sensor well on the boiler supply header.
• 2. Check connection: Ensure the sensor is fully inserted into the well and the wiring harness is firmly connected to the control board.
• 3. Inspect cable: Look for cuts, abrasions, or melted insulation along the sensor cable. Repair or replace as needed.
• 4. Replace sensor: If wiring is intact but the fault persists, replace the sensor with a Weil-McLain OEM supply sensor.