Rheem / Ruud · Furnace error code
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Get lifetime accessOnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.
Guide · FurnaceShort cycling is usually a safety opening mid-cycle (limit from low airflow, flame sensor dropping out, pressure switch opening) or a thermostat issue. Read the code and time the cycle.
Guide · FurnaceThe limit protects the heat exchanger from overheating. The fix is almost always airflow: filter, blower, ducts. Rollout switch trips are different and must be referred.
Guide · FurnaceThe common causes are a fan set to ON, a dirty filter tripping the high limit so the burners stop while the blower runs, a full condensate drain on a high-efficiency furnace, or an ignition lockout. Gas valve and burner work is blocked; stop at diagnosis and refer.