If you are standing in front of a Rheem counting blinks, stop — there is nothing to count. This control has a little digital display on the board. At rest it reads 0. While it works it shows letters: H for gas heat, C for cooling, F for continuous fan. Homeowners search those letters as error codes every winter; they are the furnace saying it is fine.
Faults are two-digit numbers, displayed a digit at a time. The one display behavior worth knowing before you reset anything: in a lockout, the display alternates — code 10 (the lockout) and the code that caused it. Two numbers, one story. Ruud furnaces run the same control and the same list.
The two rules that outrank everything on this page.
1. Smell gas? Stop reading. Leave the house and call your gas utility or 911 from outside. No code is worth diagnosing through a gas smell.
2. Never bypass a safety switch — no jumping a pressure switch, no taping a limit, no propping a rollout. Those switches are the only thing between a furnace fault and a fire or carbon-monoxide problem. This library explains codes; it does not teach repairs inside the cabinet.
Which chart is yours?
This table covers the Rheem control in the 95P-series installation instructions, shared with the R801T generation and their Ruud twins. Much older Rheem furnaces with a plain flashing LED predate this display control and are not covered here — their door chart is the reference.
7-segment display codes (no blink counting)
Rheem 95P-series and the R801T generation: the control has a small digital display. Standby reads 0; running modes read as letters. Faults show as two-digit numbers, first digit for a second, second digit for a second, then a pause.
| What you see | What the manual says it means |
|---|---|
| 0 | Standby — no faults — What the display shows when the furnace is powered and idle. Listed because people search it as a code. |
| H | Gas heat on — A mode letter, not a fault: the furnace is heating. |
| C | Compressor on (cooling or heat-pump heat) — Mode letter. On a furnace it appears when the system is in a cooling call. |
| F | Continuous fan on — Mode letter: the fan is running in continuous mode. |
| 10 | One-hour lockout — The display alternates 10 with the code that caused the lockout — read both numbers before you reset anything. Four failed ignitions in a row will do it; so will five flame losses. |
| 11 | Failed ignition — The ignition attempt did not produce proven flame. Start with the gas supply and the thermostat call; the igniter and sensor are a tech’s check. Full page → |
| 12 | Low flame sense — The flame signal is below what the control trusts. Classic coated-sensor territory. |
| 13 | Flame lost — It had flame and lost it mid-cycle. Repeated 13s become the 10 lockout. |
| 14 | Unexpected flame — Flame sensed when none was commanded. Gas code. |
| 20 | Twinning fault — Only on twinned installs: the paired furnaces are not synchronized. |
| 22 | Main limit open — The main overheat limit is open. Airflow homework, then a tech if it repeats. |
| 26 | Line and neutral reversed — Polarity fault at the supply. Electrician or tech. |
| 33 | Manual-reset limit control (roll-out) open — Rheem calls the rollout the MRLC. It does not reset itself — and it opened for a reason. Furnace off. |
| 55 | Pressure switch stuck closed when it should be open — The board catches this one before start-up: the switch reads closed at rest. |
| 57 | Pressure switch stuck open when it should be closed — The most-reported Rheem code: inducer runs, switch never proves. Vent, condensate, hose, switch — in that order. Full page → |
| 58 | Water sense circuit open — On condensing models, the water-sensing circuit is open. A controls/wiring check. |
| 59 | Water sensed — The control sees water where water should not collect. Check the drain before anything else. |
| 61 | Blower fault — blower unable to run — The control commanded the blower and it could not run. Motor or board. |
| 93 | Internal control fault — The control has diagnosed itself. Board replacement territory. |
Source: Rheem 95P Series Installation Instructions, "Diagnostics and Fault Codes". Read the document (fetched 2026-10-30).
One honesty note before the tables: codes change between control boards, sometimes inside the same brand and the same decade. Every table below names the board and the manual it was transcribed from. The chart glued inside your own blower door is the final word for your furnace — if it disagrees with this page, believe the door.
Questions
My Rheem display shows H. Is that an error?
No — H is a mode letter: gas heat on. C (cooling) and F (continuous fan) are modes too, and 0 is standby. Faults are always two-digit numbers.
The display keeps switching between 10 and another number.
That is a lockout announcing its cause: 10 is the one-hour lockout, and the other number is the fault that triggered it — 11 (failed ignition) or 13 (flame lost), most often. Diagnose the second number.
Where these meanings come from
Transcribed 2026-10-30 from the manufacturers’ own documents — not from other blogs:
- Rheem 95P Series Installation Instructions, "Diagnostics and Fault Codes" — read it