Display shows E07; heater may start and then shut down quickly, or may not start at all.

Safety first: Turn off power and gas supply to the heater. Allow the unit to cool. Do not operate the heater if the flame is unstable or lifting off the burner.

Step-by-step checks:

• Check gas supply stability: Confirm that other gas appliances are not causing large pressure drops when they start. If you suspect gas pressure issues, contact your gas supplier.
• Inspect burner tray: Remove the burner access panel and slide out the Pahlen burner tray if the design allows. Clean dust, rust flakes, and spider webs from burner ports using a soft brush and compressed air (wear eye protection).
• Clean flame sensor: Remove and clean the flame sensor rod with fine steel wool. Ensure it is positioned correctly in the flame path when reinstalled.
• Check flue and combustion air: Inspect the flue for obstructions and verify that combustion air openings are not blocked. Excessive wind or negative pressure in the equipment room can disturb the flame.
• Observe flame: After reassembly, restore gas and power, then call for heat. Through the sight glass, verify a stable, mostly blue flame that fully covers the burner. If the flame repeatedly goes out, stop and call a technician.

When to stop: Persistent flame loss indicates a combustion or gas supply problem that should be handled by a qualified gas technician.