Heater locks out with E04; blower may start but burner does not light

Safety First: Turn off power and gas. Exhaust components may be hot; allow to cool.

• Inspect venting: Check the flue outlet and intake (if applicable) for nests, leaves, or obstructions. Clear any blockage. Ensure vent terminations meet Rheem clearance requirements.
• Check blower operation: Restore power briefly and call for heat while observing the blower. If the blower does not start or is noisy, disconnect power and inspect the blower wheel for debris and the motor for signs of overheating. Replace the blower assembly if seized or not starting.
• Examine air pressure switch and tubing: Inspect the rubber tubing from the blower housing to the air pressure switch for cracks, kinks, or water. Replace tubing if damaged. Verify the switch clicks when suction is applied; if not, replace the air pressure switch.
• Reset and test: After clearing obstructions and verifying blower operation, reset the heater and test. Persistent E04 may indicate a failing control board and should be evaluated by a technician.