Ruud Furnace Code 11
Soft lockout
Failed ignition. The furnace opened the gas valve but never proved a flame. It retries with a 20-second post-purge between attempts; after the fourth consecutive failure it goes to a one-hour lockout and alternates 11 with 10.
Manual wording: “FAILED IGNITION ... This fault is displayed at the furnace control after the first failed ignition attempt. ... After four failed ignition attempts, the IFC enters one-hour lockout and the dual faults "11" and "10" are alternately displayed.”
Documented for: (-)97V, (-)96V, (-)801S/(-)801P
Likely causes, most common first
- The flame sense rod is unable to sense flame - it may need cleaning or may not be properly connected
- The gas valve may be turned off
- The igniter is not working properly, is not properly connected, or the spark location is not correct
- The furnace control may not be working properly and may need to be replaced
- The flame may not be properly spreading from the first burner to the last
What you can safely check yourself
- Check that the furnace doors are fully seated and latched.
- Check and replace a dirty air filter.
- Try one power cycle at the furnace switch or breaker to clear the lockout.
- Check the outdoor intake and exhaust terminations for snow, ice or debris.
When to call a technician
If the code returns, the flame sensor, igniter, gas valve or gas supply needs a technician. Do not open the burner compartment or touch the gas valve, flame sensor or igniter yourself.
A Ruud furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation Instructions for Upflow Condensing Modulating, Communicating Gas Furnaces - (-)97V Series (92-24161-126-04) (Rheem Manufacturing Company (Ruud brand), U97V series modulating condensing gas furnace (and U98V); TABLE 18 normal operation codes, TABLE 19 fault codes, pages 94-104) · checked 2026-08-25
- Installation Instructions for 4 Position Condensing Two-Stage, Communicating Gas Furnaces - (-)96V Series (92-24161-124-08) (Rheem Manufacturing Company (Ruud brand), U96V series and (-)(-)96MDV two-stage condensing gas furnaces; TABLE 19 normal operation codes, TABLE 20 fault codes, pages 111-120) · checked 2026-08-25
- Installation Instructions for Downflow Single Stage Gas Furnaces - (-)801S / (-)801P Downflow Series (92-24161-143-03) (Rheem Manufacturing Company (Ruud brand), U801S, U801P, (-)(-)80DSS, (-)(-)80DSP 80% single-stage gas furnaces; DIAGNOSTICS AND FAULT CODES, page 34) · checked 2026-08-25