GSW electronic gas water heater shows E005 and will not attempt ignition

Safety: Turn gas control to OFF and disconnect power. Do not bypass safety devices.

• Allow unit to cool: Wait at least 30–60 minutes for the tank and controls to cool down.
• Check water temperature setting: Ensure the setpoint on the GSW gas control is not excessively high. Adjust to 49–54°C (120–130°F) for normal use.
• Inspect for scale buildup: If the heater is older or in a hard-water area, heavy scale can cause localized overheating. Drain several litres from the drain valve to check for sediment. If heavy sediment is present, perform a full tank flush.
• Reset ECO (if manual reset type): Some GSW models have a manual reset high-limit on the gas control or thermostat well. Press the reset button firmly until it clicks. If it immediately trips again, a thermostat or gas valve fault is likely.
• Professional diagnosis: If E005 persists, the gas control valve/thermostat assembly or temperature sensor may be defective and should be replaced by a qualified technician using GSW-approved parts.