Heater attempts to ignite but shuts down with an H2 error on the display.

Safety first: Turn off gas at the appliance shutoff valve and switch off electrical power before removing any panels. If you smell gas, evacuate the area and contact your gas supplier immediately.

• Verify gas supply: Confirm that the main gas valve to the heater is fully open. Check that other gas appliances in the home operate normally; if not, there may be a gas supply issue.
• Inspect burner area: Remove the front panel and visually inspect the burner tray for rust flakes, spider webs, or debris. Gently vacuum around the burners without disturbing any wiring.
• Check ignition electrode: Locate the AstralPool ignition electrode near the main burner. Inspect the ceramic for cracks and ensure the tip is clean and positioned correctly over the burner. Lightly clean the tip with fine emery cloth.
• Check wiring connections: Ensure all spade connectors to the ignition module, gas valve, and flame sensor are tight and free of corrosion.
• Attempt restart: Restore power and gas, then call for heat. Observe through the sight glass: you should see sparking followed by flame. If sparking occurs but no flame appears, gas pressure or the gas valve may be at fault.

If H2 persists, a licensed gas technician should measure gas pressure and test the ignition control and gas valve.