Electronic gas water heater shows E05; unit may not respond to temperature changes or may shut down intermittently.

Safety: Disconnect power before accessing wiring. Turn gas control to OFF.

• 1. Locate thermistor: On American Water Heaters electronic models, the tank temperature sensor is typically mounted in a well on the tank or clipped to the tank surface under insulation. Remove the access cover and insulation carefully.
• 2. Inspect wiring: Check the sensor harness for cuts, pinches, or melted insulation. Ensure the connector is fully seated on the control board and free of corrosion.
• 3. Measure resistance: Disconnect the sensor and measure its resistance with a multimeter. Compare to the temperature/resistance chart in the service manual (for example, around 10kΩ at 77°F, depending on model). If the reading is open, shorted, or far off spec, replace the sensor.
• 4. Check for moisture: Look for water intrusion around the sensor well or wiring. Dry any moisture and correct leaks before reassembly.
• 5. Control board evaluation: If a known-good sensor still results in E05, the control board (integrated in the gas control valve on many models) may be defective and require replacement by a qualified technician.