Rheem furnace — Rheem residential gas furnaces covered by the published technical FAQ Error Codes Directory

Rheem furnace one-blink lockout: four trials or four flame failures

Rheem publishes the one-blink code as no flame sensed after four ignition trials, or four flame failures during one call for heat. Those are two different histories: in the first the burner never established a flame, and in the second it lit four times and the signal was lost each time. To clear it, Rheem has the owner interrupt the 115 volt supply, or switch the thermostat off, for a count of five to ten seconds. Applies to: Rheem residential gas furnaces covered by the published technical FAQ This code and reset method come from Rheem's published gas furnace technical FAQ and apply to the Rheem furnaces it covers. Ruud furnaces share much of the Rheem platform but their own literature governs, and a single flash on another manufacturer's control means something else entirely. Owner-safe checks: Stand where you can hear the furnace and note whether the burner is audible on each attempt before the lockout. | Count the blinks and confirm the pattern repeats rather than changing between cycles. | Check that other gas appliances in the house work, without operating a valve or opening the furnace cabinet. | Confirm the filter is clean and every supply register is open, since airflow faults produce a different code. | Clear the lockout once, by interrupting the 115 volt supply or the thermostat for a count of five to ten seconds. Qualified technician: The same lockout returning after one reset with the gas supply confirmed. | A two-blink or four-blink pressure-switch pattern, which is a separate combustion-safety service path. | Any work on the flame sense rod, gas valve, or manifold pressure, all of which need the burner compartment opened. | Suspected supply polarity or grounding problems, which are electrical rather than heating work. | Any smell of gas, which is an evacuation and an emergency call rather than a service request.