Water heater displays E1 and burner or elements do not turn on

Safety first: Disconnect electrical power and shut off gas supply (for gas models). Allow the heater to cool.

• Locate the inlet sensor: On Giant water heaters with digital controls, the cold inlet temperature sensor (thermistor) is typically threaded or clipped near the cold water inlet nipple or inside the front service panel attached to the inlet piping.
• Inspect wiring: Follow the two‑wire harness from the inlet sensor to the control board. Look for cuts, pinches, or melted insulation. Repair or replace damaged wiring.
• Check connector: Unplug the sensor connector at the control board, inspect for corrosion or bent pins, and reconnect firmly.
• Test the sensor: Using a multimeter set to resistance (ohms), measure the thermistor resistance at room temperature. Compare to Giant’s thermistor chart (typically 10–50 kΩ at 25°C). If reading is open (OL) or near 0 Ω, replace the sensor.
• Replace parts as needed: If wiring and sensor test good but E1 remains, the Giant electronic control board may be faulty and should be replaced by a technician.