F04 error displayed, no hot water, unit indicates ignition or flame failure on gas model

Safety first: Turn OFF gas at the shutoff valve and turn the gas control knob to OFF. Turn OFF electrical power at the breaker.

Steps to check (gas models):

• Remove the burner access cover to access the burner assembly, igniter, and flame sensor.
• Inspect the burner for rust, debris, or spider webs. Clean with a soft brush and compressed air (outdoors if possible).
• Locate the flame sensor (usually a small metal rod in the flame path). Gently clean it with fine steel wool or emery cloth to remove oxidation.
• Inspect the igniter for cracks or damage. Ensure the igniter wiring is intact and firmly connected.
• Verify the gas shutoff valve is fully open and that other gas appliances in the home are working normally (to rule out supply issues).

Reassembly and test:

• Reinstall the burner assembly and access cover securely.
• Restore gas and power, then attempt to start the heater.
• If F04 persists, the gas control valve or ignition module on the control board may be defective and should be replaced with the correct Whirlpool OEM part.

Warning: If you smell gas or suspect a leak, shut off gas immediately and contact a qualified technician. Do not attempt repeated ignition.