Heater displays E05 and will not fire; blower may start then stop

Safety: Turn off power and gas. Exhaust components can be extremely hot; allow full cool-down.

• Inspect vent termination: Go outside and check the exhaust vent outlet. Remove any leaves, nests, or obstructions. Ensure the vent cap is not crushed or blocked.
• Check vent length and slope: Compare your installation to the SunHeater installation manual. Excessive vent length, too many elbows, or improper slope can cause E05. Correct any obvious installation errors if accessible.
• Examine flue temperature sensor: Inside the heater, locate the Flue Temperature Sensor mounted near the exhaust outlet. Inspect wiring for heat damage. Test the sensor resistance against the service chart (if available). Replace if out of specification.
• Look for soot: Remove the burner access panel and visually inspect the heat exchanger fins. Heavy black soot indicates poor combustion and restricted flue passages. Do not operate the heater in this condition; have a professional clean the heat exchanger and check combustion.
• Reset and test: After clearing obstructions and verifying the sensor, restore power and gas. If E05 returns immediately, stop using the heater and contact a qualified technician to evaluate venting and combustion.