Bradford White power vent or high-efficiency gas water heater displays E04 and will not run.

Safety: A tripped rollout or spill switch indicates a potentially dangerous flue gas condition. Turn off gas and power and do not operate the heater until the cause is found.

Steps:

• Check rollout/spill switches: Locate the manual reset rollout or spill switches near the burner or draft hood. If equipped with a reset button, press firmly to reset. If they immediately trip again, stop and call a professional.
• Inspect exhaust vent: Verify the exhaust vent is not blocked or restricted. Check for crushed sections, disconnections, or obstructions at the termination.
• Examine combustion chamber: Look for signs of flame rollout (soot, discoloration, melted wiring). If present, do not relight. Professional service is required.
• Check high-limit sensor: Some models use a flue or tank temperature limit sensor. If the sensor is open and will not reset, it may need replacement.

Important: Because this fault can indicate serious combustion or venting problems, most homeowners should not attempt further diagnosis beyond visual checks. Contact a licensed technician to verify gas pressure, combustion, and venting.