Rheem R801SA furnace code 11: Failed ignition
Professional repair
What does code 11 mean on a Rheem R801SA (801S downflow) furnace display? Code 11 records failed ignition. After four consecutive failed ignition attempts, the display alternates 10 and 11 and the furnace enters a one-hour lockout.
This condition involves the gas or combustion side. If you smell gas or a CO alarm sounds: leave, then call your gas utility. Diagnostic info here is reference — combustion repairs are for licensed technicians. All six emergency signs →
Safe checks before calling
Confirm the thermostat is set to HEAT with the setpoint above room temperature, and note whether the furnace tries to light at all. Do not restart it repeatedly.
Igniter testing, flame-current measurement, gas-pressure checks and grounding or polarity verification are technician tasks. They require live-circuit and gas-system work that homeowners should not attempt.
Possible causes
- Gas supply pressure outside what the burner needs TECH
- Poor grounding or reversed polarity affecting flame detection TECH
- Contaminated flame sensor rod weakening the flame signal TECH
Parts for this code
No model-verified part number is listed here. Have the fault diagnosed and the correct part matched to your furnace before ordering.
Questions about this code
What does code 11 mean on a Rheem R801SA (801S downflow) furnace display?
Code 11 records failed ignition. After four consecutive failed ignition attempts, the display alternates 10 and 11 and the furnace enters a one-hour lockout.
How do I fix Rheem R801SA furnace code 11?
Leave the furnace in lockout and book service. The technician watches an ignition attempt, finds which step fails, and corrects that step. Cleaning or swapping parts without that test is guesswork. Do not keep restarting to force ignition.
How much does it cost to fix Rheem R801SA furnace code 11?
The failed ignition step determines the work. Correcting gas pressure or wiring involves different labor from replacing a component, so the technician needs to diagnose it first.
Applies to
R801SA / 801S downflow single-stage 80% furnace with PSC motor
Different Rheem generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Installation Instructions for Downflow Single Stage Gas Furnaces, p.34
Verified against Rheem 801S Series Installation Instructions — OEM143-14 mirror, p.34
Verified against Rheem 801S Series Installation Instructions — OEM143-14 mirror, p.35
Last verified 2026-10-07 · page updated 2026-10-07 · how we verify
Related Rheem furnace codes
These codes use the same rheem 801s downflow single-stage control (manual 92-24161-143-14) system.