Heater display shows E04 and the unit will not fire; fan may run but shuts down quickly.

Safety first: Turn off power and gas. Exhaust faults can lead to carbon monoxide buildup. Do not operate the heater until the venting is verified clear and safe.

• Inspect outdoor vent: Check the Kripsol heater exhaust terminal for leaves, nests, snow, or other obstructions. Clear any blockage and ensure the vent cap is intact.
• Check for recirculation: Make sure the exhaust outlet is not too close to walls, overhangs, or other structures that could cause flue gases to recirculate into the intake.
• Inspect flue sensor: Locate the Kripsol flue gas temperature sensor on the exhaust manifold. Check wiring and connector for heat damage. With power off, test the sensor resistance and compare to the service chart; replace if out of range.
• Internal inspection: If accessible, remove the top cover and inspect internal baffles and flue passages for soot or scale buildup. Heavy deposits require professional cleaning.
• Reset and test: After clearing obstructions and verifying the sensor, restore power and gas. If E04 returns, have a certified technician evaluate the vent design and heat exchanger.