What does Ruud code 12 mean?
Ruud furnace code 12 means the flame-sensor signal is below the acceptable range on the supported control family. Confirm the model number and diagnostic chart inside the furnace door before replacing parts.
What causes Ruud code 12?
- A dirty flame sensor
- Poor furnace grounding or reversed polarity
- Low gas pressure or an unstable burner flame
Can I troubleshoot Ruud code 12?
- Turn furnace power off and confirm its access panel is fully seated.
- Try one reset and note whether the burners light briefly before shutting off.
How much does Ruud code 12 cost to fix?
A flame sensor cleaning or replacement typically costs between $100 and $400 nationally.
When should I call a technician?
Call a technician if flame drops out again; flame current and combustion should be measured.
Sources and model scope
Fault codes vary by model and control board. Confirm the diagnostic chart inside your furnace panel or the official manual before acting.
Scope used here: Rheem/Ruud RGFG-family controls using the documented two-digit diagnostic table.
- Rheem Manufacturing Company: RGFG Series Gas Furnace Installation Instructions and Diagnostic Codes
92-24161-104-06 · Rheem/Ruud RGFG-family furnace controls; confirm the unit model and its door chart before applying a code meaning.
Compiled by Warmlo Editorial · Reviewed August 2026
This is general information, not professional advice. Gas, electrical, and combustion repairs can be dangerous — when in doubt, call a licensed technician.