Ruud Furnace Code C
Status
Cooling mode. The furnace blower is responding to a cooling (or heat-pump) call from the thermostat. Lower-case "c" is low-stage cooling, upper-case "C" is high-stage cooling.
Manual wording: “COOLING MODE ... This code is displayed anytime there is a call for cooling.”
Documented for: (-)97V, (-)96V; on (-)801S/(-)801P the same C means COMPRESSOR ON (cooling or heat-pump heat)
Likely causes, most common first
- Normal cooling operation
What you can safely check yourself
- Nothing to do - this is normal operation.
When to call a technician
No action needed unless the air conditioner is not actually cooling.
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