Rheem/Ruud furnace status codes, decoded
Newer Rheem and Ruud furnaces show two-digit codes on a 7-segment display. Normal characters first — 0 = standby, H = heating, C = cooling, F = fan — they're status, not faults. The fault set: 10 = one-hour ignition lockout, 11 = failed ignition, 12 = weak flame, 13 = flame lost mid-cycle (all four usually trace to a dirty flame sensor, igniter, or gas supply), 22 = main limit open (airflow/filter), 26 = reversed polarity (electrician), 33 = rollout open (SAFETY), 45/55/57 = pressure-switch faults (venting/inducer/condensate), 61 = blower motor fault, 93 = control board failure (not resettable — board replacement).