HeatingCodes

Rheem and Ruud furnace fault codes (801T series)

By Jason Dearmin · Last reviewed November 14, 2026

Furnaces with this control have a seven-segment display on the board. It shows a single character in normal operation and a two-digit number when there is a fault.

What this table coversCodes from section 14 (Diagnostics and Fault Codes) of the Rheem installation instructions for the (-)801T upflow/horizontal series and (-)(-)80MSX series single-stage furnaces. Rheem and Ruud also build other furnaces with different controls.

How to read the display

With no faults, the display reads 0 in standby. During operation it shows a letter: C for cooling or heat pump operation, F for continuous fan and H for gas heating. A fault is shown as a two-digit number.

Each two-digit number is shown one digit at a time. The first digit is displayed for one second, then the second digit for one second, then there is a half-second pause and the cycle repeats. When two faults are present, the display alternates between them with a short bar between. Rheem says that after four failed ignitions the display alternates 10 and 11, and that after five flame losses in a row it alternates 10 and 13. Code 10 means a one-hour soft lockout.

Rheem / Ruud code table

CodeMeaningWhat the document says
0 Standby
C Compressor on (cooling or heat-pump heat)
H Gas heat on
F Continuous fan on
10 One-hour lockout (soft lockout) Alternates with the code for the fault that caused the lockout, such as 11, 13, 14 or 61. The lockout resets automatically after one hour. Full explanation
11 Failed ignition Four failed ignition trials in a row cause a one-hour lockout, shown as 10 and 11. Full explanation
12 Low flame sense
13 Flame lost Flame lost five times in one heat call causes a one-hour lockout, shown as 10 and 13.
14 Unexpected flame The control enters a one-hour lockout, shown as 14 and 10.
20 Twinning fault
22 Main limit or HALC open If the main limit stays open more than 150 seconds during a gas heat call, the display alternates 61 and 22. Full explanation
26 Line and neutral reversed
33 MRLC (manual reset limit control, also called rollout) open
55 Pressure switch stuck closed when it should be open
57 Pressure switch stuck open when it should be closed If the low pressure switch does not close after 60 seconds of inducer operation, the control starts a five-minute soft lockout.
61 Blower fault: blower unable to run Declared when the main limit has been open for more than 150 seconds. Full explanation
93 Internal control fault A hard lockout that cannot be cleared by cycling the heat call.

Source: Rheem installation instructions 92-24161-144-08, Diagnostics and Fault Codes.

Detailed explanations

SafetyThese tables describe what the manufacturer documents say. Gas, combustion, refrigerant and line-voltage repairs are for licensed professionals. If you smell gas, leave the building and call your gas utility or 911. Safety disclaimer.

Sources