Zodiac gas pool heater will not ignite; display shows E01 shortly after a call for heat.

Safety first: Turn off power at the breaker and shut off the gas supply valve before opening the heater. Allow the heater to cool completely.

• Check gas supply: Verify the gas valve to the heater is fully open. Confirm other gas appliances are working. If not, contact your gas supplier.
• Inspect the igniter: Remove the front panel and locate the hot surface igniter assembly. Look for cracks, heavy white deposits, or broken ceramic. If damaged, replace the igniter with a Zodiac-compatible hot surface igniter.
• Clean the flame sensor: If the flame sensor is separate from the igniter, gently clean the metal rod with fine emery cloth or a Scotch-Brite pad to remove oxidation. Do not sand aggressively.
• Check wiring connections: Inspect the harness from the ignition control board to the igniter and flame sensor. Reseat any loose connectors and look for burned or brittle wires.
• Reset and test: Restore power and gas, then call for heat. If E01 returns after cleaning and verifying gas supply, the igniter or ignition control board may need replacement.

If you smell gas or see signs of scorching inside the heater, stop and contact a qualified pool heater technician.