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Rheem / Ruud R801T Ultra Low NOx Furnace Codes
Ultra Low NOx models only (model numbers ending in MUA or similar). The standard R801T has a shorter code list; see its own chart.
| Code | Meaning | What to check |
|---|---|---|
| 10 | 1-hour lockout. | How to fix → |
| 11 | Failed ignition. | How to fix → |
| 12 | Low flame sense. | How to fix → |
| 13 | Flame lost. | How to fix → |
| 14 | Unexpected flame. | Gas valve leaking through or a shorted flame sense circuit. How to fix → |
| 22 | Main or auxiliary limit open. | How to fix → |
| 26 | L1 and neutral reversed. | Swap line and neutral. |
| 33 | Rollout switch open. | How to fix → |
| 34 | Induced draft motor overcurrent. | |
| 42 | Flame LED not detected. | |
| 43 | Ignition pressure switch closed when it should be open. | How to fix → |
| 55 | Combustion pressure switch closed when it should be open. | How to fix → |
| 56 | Ignition pressure switch open when it should be closed. | How to fix → |
| 57 | Combustion pressure switch open when it should be closed. | How to fix → |
| 58 | Water sensor jumper not attached. | |
| 61 | Blower fault. | |
| 71 | Inducer fault. | |
| 74 | Gas inlet pressure switch open. | Check inlet gas pressure. |
| 75 | Venturi air inlet pressure switch open. | |
| 93 | Control fault (hard lockout). | |
| 96 | Flame circuit fault. | How to fix → |
| 97 | Gas valve circuit fault. |
How to read the codes
- 0 means standby with no faults. Letters show the current call: C cool or heat-pump heat, H gas heat, F continuous fan, CL inducer calibration.
- Two-digit codes show the first digit for one second, then the second for one second, then a half-second pause. Two faults alternate, with the top segment lit between them.
- Most lockouts clear once the fault is fixed and power is cycled. The one-hour lockout resets itself; code 93 is a hard lockout.
Codes point to a circuit, not a part. Test before replacing anything, and never jumper a limit, rollout or pressure switch to keep a furnace running. Gas and line-voltage work is for trained technicians.
Source: Rheem Installation Instructions, (-)801T Upflow Series Ultra Low NOx single-stage gas furnaces, 92-24161-164-01, Diagnostics. The "meaning" column follows the manufacturer's wording; "what to check" is our field summary. Always go by the label on the furnace you're working on.
Related
- How to read furnace LED flash codes
- Furnace pressure switch troubleshooting
- Flame sensor microamps and cleaning
Other brands
- Lennox Merit ML180UH (80% single-stage)
- Carrier 58CVA / 58CVX (80% variable-speed two-stage)
- Rheem / Ruud R96V / 96MDV (96% two-stage communicating)
- Goodman / Amana GR9S80 / GD9S80 (80% single-stage)
- Trane / American Standard S9X1 / S9X2 / S9B1 (96% condensing)
- Lennox SL280UHV (80% two-stage variable speed)
- Goodman / Amana / Daikin GM9S96 / GC9S96 / GM9S92 (96% and 92% condensing, single-stage)
- Carrier 59TP6C two-stage condensing with InteliSense (Performance series)
- Lennox G60DF / G60DFV (older two-stage SureLight boards 18M3401, 46M9901, 18M9901, 49M5901)
- Lennox G60UH / G60UHV (SureLight boards 100869 and 100870)
- Rheem / Ruud 802V / 80MDV (80% two-stage communicating, ECM blower; model numbers (-)802V and (-)(-)80MDV)
- Trane / American Standard S8B1 / S8X1 / S8X2 (80% single-stage and two-stage)
- Goodman / Amana GMVC96 / GCVC96 (96% two-stage variable-speed, *MVC96*BA and *CVC96*BA)
- Goodman / Amana GMVS96 / AMVS96 U-revision (96% variable-speed with analog pressure sensor, model numbers GMVS96*U and AMVS96*U)
- Goodman / Amana GMVM96 / GCVM96 / AMVM96 / ACVM96 (96% modulating, model numbers *MVM96 and *CVM96)
- Rheem / Ruud R801T / 80MSX (80% single-stage, constant-torque blower; model numbers (-)801T and (-)(-)80MSX)
- Rheem / Ruud 802P / 80MDP (80% two-stage, model numbers (-)802P and (-)(-)80MDP)
- Rheem / Ruud 802T / 80MDT (80% two-stage with constant-torque blower, model numbers (-)802T and (-)(-)80MDT)
- Rheem / Ruud 801S / 801P / 80MSS / 80MSP (80% single-stage, model numbers (-)801S, (-)801P, (-)(-)80MSS and (-)(-)80MSP)
- Carrier 58STA / 58STX (80% single-stage, 4-way multipoise)
- Carrier 58SB0A / 58SB1A (single-stage, non-condensing)
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