Unit powers on but does not heat water; display shows E1 shortly after a hot water tap is opened.

Safety first: Turn OFF the circuit breaker supplying the Eemax water heater and verify power is off with a non-contact voltage tester. Close the cold water supply valve before opening the unit.

Steps to check and correct:

• Remove the front cover of the Eemax heater (typically Phillips screws at the corners). Keep track of screws.
• Locate the inlet thermistor/temperature sensor on the cold water inlet pipe or heat exchanger inlet. It is usually a small probe with two wires going to the control board.
• Inspect the sensor wiring harness and connector at the control board for corrosion, loose pins, or broken wires. Reseat the connector firmly.
• With power still OFF, disconnect the thermistor and measure its resistance with a multimeter. Compare the reading to the Eemax service chart for the current water temperature. A reading that is open (OL) or shorted (near 0 Ω) indicates a failed sensor.
• If the thermistor is defective, replace it with an OEM Eemax inlet thermistor. Apply thermal paste if specified and secure it tightly to the pipe or well.
• Inspect for scale buildup around the sensor area; flush the unit if heavy scale is present.
• Reassemble the cover, open the cold water supply, check for leaks, then restore power at the breaker.
• Open a hot water tap and verify that the E1 code is cleared and water heats normally.

If E1 persists after sensor replacement and wiring checks, the control board may be misreading the sensor and should be evaluated or replaced by a qualified technician.