Boiler shows E7; may not respond correctly to return water temperature

Safety first: Turn off power and let the boiler cool.

• Locate the return sensor: Typically mounted on or inserted into the return piping entering the boiler.
• Inspect and reseat: Check the sensor body and wiring for damage. Reseat the connector at both the sensor and the control board.
• Check for water leaks: Any leak at the sensor well or nearby fittings can cause corrosion and sensor failure. Repair leaks before replacing the sensor.
• Test and replace: Measure resistance and compare to the Ruud chart. Replace the sensor if readings are out of range or if the code persists after wiring checks.