Display shows E1 and burner or heating elements do not activate

Safety first: Turn off power at the breaker and close the cold water supply. Allow the heater to cool before touching any internal components.

Steps to check:

• Locate the inlet water temperature sensor (inlet thermistor) on the cold water inlet pipe inside the CTC water heater. It is usually clipped or threaded into a sensor well with two small wires leading to the control board.
• Inspect the sensor wiring for cuts, burns, or disconnections. Reseat the connector at the sensor and at the main control PCB.
• If you have a multimeter, disconnect the thermistor and measure its resistance at room temperature. Compare to the CTC service manual chart (typical NTC thermistors are around 10k–50k ohms at 25°C). Infinite or near-zero resistance indicates a failed sensor.
• Replace the inlet thermistor if readings are out of range or if the sensor is physically damaged.
• If a known-good thermistor is installed and wiring is intact but E1 remains, the thermistor input circuit on the main control PCB may be defective and the board will need replacement.

Note: Always refill and purge air from the heater before restoring power.