Boiler shows E5 and will not fire; may indicate a sensor out of range or wiring fault.

Safety first: Turn off power to the boiler before accessing wiring or sensors.

• Step 1 – Locate supply sensor: Find the supply (outlet) water temperature sensor on the boiler piping or heat exchanger. It is typically a small probe with two wires.
• Step 2 – Inspect wiring: Check the sensor wires for cuts, abrasions, or signs of overheating. Ensure the connector at the sensor and at the control board is fully seated.
• Step 3 – Check sensor resistance (if equipped): With power OFF, disconnect the sensor and measure its resistance with a multimeter. Compare to Bradford White’s temperature/resistance chart (often around 10kΩ at 77°F for many NTCs). An open or shorted reading indicates a bad sensor.
• Step 4 – Replace sensor if faulty: If resistance is out of spec, replace the supply temperature sensor with the correct Bradford White part number.
• Step 5 – Inspect control board: If the sensor tests good and wiring is intact, the control board’s sensor input may be defective and require replacement by a technician.

Tip: Always route sensor wires away from high-voltage lines to avoid electrical interference.