Rheem Air Conditioner Error Codes List: Every Code Explained
Every Rheem air conditioner error code we could verify against Rheem's own documentation — what it means, what usually causes it, and the first fix to try — in one table. Codes differ between model series, so treat your model's tech sheet as the final word.
How to read and retrieve error codes on Rheem air conditioners
Every code on this page lives in one place: the dual 7-segment display on the ICC inside the outdoor unit. Status letters and codes are read directly off that display (the variable-speed manual warns that codes must be read from the correct side to avoid a reading error), and an L-lockout shows as the letter L alternating with its two digits. History is built in: the JEC controls have a Fault Recall mode — press TEST and SW2 at the same time with insulated probes and the ICC scrolls the stored faults, each shown once with the display's top and bottom segments lit on entry and exit, and the same button pair clears the fault history. A second reporting path exists on conventionally wired JEC systems: the ICC's L terminal. Wired to an L-compatible thermostat, it flashes a short summary list indoors — Flash 1 long run cycle or low pressure, Flash 2 high pressure trip, Flash 3 short cycling, Flash 4 locked rotor, Flash 5 compressor will not run/open circuit, Flash 6 open start circuit, Flash 7 open run circuit, Flash 8 control mis-operation, Flash 9 low control voltage. Those flashes are a digest of the display codes, not a second code system: the number to quote a technician is always the one on the outdoor display. On fully communicating systems the same events also surface at the wall control — on EcoNet variable-speed systems as A/T alert numbers paired with the display codes (the (-)P20 manual pairs, e.g., 29 with T923 and its lockout with A923) — while a conventionally wired system's homeowner display shows none of it, which the JEC manual states plainly: fault history is not available when the unit runs on a conventional thermostat beyond what the L terminal flashes.
The complete Rheem air conditioner error code list
| Code | Meaning | Most likely cause | First fix |
|---|---|---|---|
| 0 | Standby — not a fault (both ICC generations): the display reads 0 when line voltage and 24 VAC are present at the ICC and there is no command for unit operation | Normal idle state between cooling calls | No repair needed. If a cooling call is active and the display stays at 0, the call is not reaching the outdoor control — thermostat/control wiring is technician diagnosis |
| 01 | Long run time (two-stage ICC) — the compressor has continuously run for more than 18 hours in the cooling mode | The manuals' stated causes: low refrigerant charge, air ducts with substantial leakage, a dirty indoor air filter, or a dirty outdoor coil — anything that makes the unit unable to satisfy the call | Owner checks: filter and outdoor coil cleanliness. Charge and duct-leak diagnosis are certified-technician work. 01 is the unit telling you it ran all day and lost |
| 02 | High side fault / high pressure control open (two-stage ICC) — the compressor limit (high-pressure control) has opened four times within a call for operation; the chart cross-references codes 21, L21, 29 and L29 | Repeated high-pressure events within one demand — in cooling the manuals name a dirty outdoor coil or an outdoor fan not running; also a liquid-line restriction or excessive refrigerant charge | Treat as code 29 that has already repeated four times: coil/fan/airflow first, then certified pressure diagnosis. Do not keep restarting the unit into high pressure |
| 03 | Short cycling (two-stage ICC) — the ICC detects the run time of each of the past four compressor cycles was less than three minutes | The manuals' stated checks point at the demand signal: thermostat wire connections (R, C, 1 and 2), or the thermostat located in the zone too close to a discharge grille, so supply air satisfies it almost immediately | Note the pattern for the technician — what starts and stops it. Short cycling is a compressor-life fault, not a nuisance code |
| 05 | Open circuit — compressor will not run (two-stage ICC): the ICC has received a command for unit operation but no current is present in the start and run circuits; in the chart's fuller wording, the ICC has had a protector trip for longer than 4 hours. The ICC retries every 5 minutes for four attempts, then every 20 minutes for up to four hours | The manuals' stated checks: a damaged, miswired or wrong run capacitor; broken wires, loose connectors or a miswired compressor; compressor windings open; or an open compressor internal protector | Technician circuit diagnosis; a four-hour open is a failed component, not a transient |
| 06 | Compressor open start circuit (two-stage ICC) — the ICC detects current in the run circuit but not in the start circuit of the compressor | The manuals' stated checks: a damaged, miswired or wrong run capacitor; broken wires, loose connectors or a miswired compressor; compressor windings | Technician start-circuit work. Four occurrences in one compressor call escalate to L6 |
| 07 | Compressor open run circuit (two-stage ICC) — the ICC detects current in the start circuit but not in the run circuit of the compressor | The manuals' stated checks mirror code 06: run capacitor, wiring/connectors, compressor miswiring, windings | Technician diagnosis, as for 06. Four occurrences in one call escalate to L7 |
| 09 | Low secondary volts (both ICC generations) — the secondary voltage at R and C is below 18 VAC | The manuals' stated causes: an overloaded control transformer, or low line voltage dragging the 24 V supply down | Technician low-voltage diagnosis. A starved control drops calls and logs phantom faults |
| 21 | Low pressure control open (both ICC generations) — the ICC detects the LPC is open. Note: the LPC is ignored for the first 90 seconds of compressor operation (and during defrost on heat pumps), so a genuine 21 is read in steady operation | In cooling, the manuals' stated causes: low refrigerant charge, a frozen indoor coil, a dirty indoor coil or filter, the indoor blower not running, or an expansion valve not operating correctly | Owner checks: filter clean, indoor blower running, no ice on the indoor coil. Charge and expansion-valve work are certified-technician work. Three opens in one call escalate to the L21 lockout |
| 27 | Low line voltage or no line voltage fault (two-stage ICC list; on the variable-speed control the same event is AC input under voltage, inverter alert A907) | Supply voltage missing or sagging at the unit: disconnect/breaker state, utility sag, or supply wiring dropping voltage under load | The manuals' stated actions: check incoming line voltage to the disconnect and unit, and check wiring connections. Recurring sags are electrician work |
| 28 | High line voltage fault (two-stage ICC list; variable-speed control: AC input over voltage, inverter alert A906) | Utility supply voltage genuinely too high, or a supply problem (e.g. a lost neutral) pushing voltage up | Check line voltage, per the manuals. Sustained over-voltage is a utility/electrician problem — do not keep running the unit into it |
| 29 | High pressure control open (both ICC generations) — the ICC detects the HPC is open (variable-speed control pairs it with inverter alert T923) | In cooling, the manuals' stated causes: a dirty outdoor coil or an outdoor fan not running; also a liquid-line restriction or excessive refrigerant charge | Owner checks: outdoor coil cleanliness and fan operation. Restriction and charge work are certified-technician work. Three opens in one call escalate to L29 |
| 30 | Fuse open (two-stage ICC) — the ICC detects its on-board 3-amp fuse is open | The manuals' stated cause: low-voltage wiring at R and C damaged or miswired, shorting the control circuit | A technician repairs the low-voltage short first and only then replaces the fuse — a fuse replaced into a live short just opens again |
| 80 | Low air flow (two-stage ICC) — the ICC detects the indoor unit is not providing the minimum airflow the outdoor unit requires | The manuals' stated cause: a misapplied/wrong indoor air mover — the indoor unit is not the approved match for the outdoor unit | Verify the indoor unit is the approved match; the manuals' stated fix is to replace it with a properly sized unit. Airflow measurement is technician work |
| 83 | Condenser (outdoor) coil temperature fault (both ICC generations) — the coil sensor detects an abnormally low or high coil temperature | The manuals' stated causes: a failed coil thermistor, or a sensor not installed correctly on the control | A technician checks the sensor's installation on the control and replaces the sensor if it reads out of range |
| 84 | Outdoor ambient temperature fault (both ICC generations; variable-speed control: alert T952) — the ambient sensor detects an abnormally low or high outdoor temperature reading | A failed ambient thermistor, or a sensor baking in an abnormally hot placement (the manuals suggest checking unit placement and re-reading when ambient drops) | Check placement, then sensor replacement — technician work. Ambient readings steer capacity and (on heat pumps) defrost decisions, so a lying sensor corrupts both |
| 93 | Internal control fault (two-stage ICC wording: 'the control is not functioning properly — check control for proper system operation, replace control'; on the variable-speed control the same display is configuration data restore failure, EcoNet alert A950) | An internal failure of the ICC, or (variable-speed) its stored configuration data failing to restore | Control replacement is technician work, and on communicating models the memory/model data must be preserved or transferred or the new control adds a d1 to the 93 |
| C | Cooling operation — an operating display, not a fault (both ICC generations): lower-case 'c' = the unit has received a command for first-stage cooling, upper-case 'C' = a command for second-stage cooling; a FLASHING letter means the 3-minute anti-short-cycle timer or the 30-second minimum run timer is active | A normal cooling command from the thermostat — the stage shown is the stage the system is running | No repair needed; a flashing letter simply means the unit is waiting out its timer — wait for it to expire (a technician can defeat the delay with the TEST button) |
| L4 | Locked rotor lockout (two-stage ICC) — the ICC detects four consecutive protector trips with an average run time under 15 seconds each and has locked the compressor out (display alternates/flashes L and 04). This active-protection mode must be manually reset | The manuals' stated causes: a bad run capacitor, low line voltage, excessive refrigerant in the compressor, or seized compressor bearings | Technician start-circuit and compressor diagnosis BEFORE the manual reset (cycle line voltage, cycle 24 VAC at R/C, or press TEST for 1 second — the manuals' three reset methods). Resetting into a locked rotor just repeats the four damaging attempts |
| L6 | Open start circuit lockout (two-stage ICC) — the open-start condition has occurred four times in one compressor call and the ICC has locked the compressor out (display flashes L, then 06). This active-protection mode must be manually reset | The code 06 fault, unhealed across four attempts | Repair the start circuit first, then reset (line voltage, 24 VAC at R/C, or TEST for 1 second) — the lockout is the control refusing a fifth attempt |
| L7 | Open run circuit lockout (two-stage ICC) — the open-run condition has occurred four times in one compressor call; compressor locked out (display flashes L, then 07). Must be manually reset | The code 07 fault, repeated four times in one call | Repair before reset, as for L6 |
| L21 | Active protection — low pressure control trip lockout (two-stage ICC: display alternately flashes L and 21; the variable-speed control writes the same event as flashing 21L): the LPC has opened three times in the same cooling operation and the ICC has locked out the compressor. Must be manually reset | The code 21 family, three times in one demand | Fix the 21 cause (charge, airflow, ice, expansion valve) before the manual reset (line voltage, 24 VAC at R/C, or TEST for 1 second); the ICC locked the compressor out specifically to stop a fourth low-pressure run |
| L29 | Active protection — high pressure control trip lockout (two-stage ICC: display alternately flashes L and 29; variable-speed control writes it flashing 29L, EcoNet alert A923): the HPC has opened three times in the same call for operation and the ICC has locked out the compressor. Must be manually reset | The code 29 family, three times in one demand | Correct the 29 cause before the manual reset (line voltage, 24 VAC at R/C, or TEST for 1 second) — a high-pressure lockout is the compressor's protection against its most damaging operating state |
| P | Protector trip (two-stage ICC) — a command for compressor operation is present but no current is measured to the compressor: the compressor's motor protector is open | The manuals' stated causes: motor protector open, or line voltage disconnected | Let the compressor cool; why the protector opened is technician diagnosis. Repeated protector trips escalate — four consecutive short trips become lockout L4 |
| d1 | No shared data / no model data (both ICC generations) — the ICC has no valid shared (model) data, so it does not know what unit it is controlling; the chart's fuller wording sends you to the memory card label ('electronics group to describe' codes d1-d8) | The memory/model data card is missing, disconnected, or was not transferred when the control was replaced | The manuals' stated fix: replace the memory card with the correct system information for the exact model. Never borrow another unit's card |
| d3 | Airflow CFM mismatch (two-stage ICC) — the indoor air mover (air handler/furnace) cannot supply the required airflow for proper system operation | The manuals' stated cause: a misapplied/wrong indoor air mover | The manuals' stated fix: replace with a properly sized air handler/furnace. d3 is a matched-system complaint, not a dirty-filter code — the unit is saying the indoor partner itself is wrong |
| d4 | (Device) memory card invalid for device (two-stage ICC) — the data in the memory card inserted into the control board does not match the data in the control | A wrong model's card fitted (typically after a control change), or no card present | The manuals' stated checks: check the memory card to ensure it matches the device, and check whether a memory card is present at all |
| d8 | Old shared data (two-stage ICC) — the system data the control is holding is obsolete | Stored shared/model data superseded — the control's data no longer matches the current system configuration data | The manuals' stated fix: if the system will not operate, order a new memory card to update the system information |
| t | Test mode (two-stage ICC) — the ICC is in TEST mode, entered from the control's TEST button | A technician has put the control into its test mode (TEST also resets an active-protection lockout and defeats the short-cycle delay) | No repair needed — a service state, not a fault. The unit attempts to start when TEST is pressed and released |
How to reset / clear error codes on Rheem air conditioners
Ordinary ICC fault codes clear themselves once the fault condition is gone — the display returns to its operating letter or to 0 (standby). The exception is Rheem's Active Protection family: the L-lockouts (L4 locked rotor, L6 open start circuit, L7 open run circuit, L21 low-pressure trip, L29 high-pressure trip) latch the compressor out and, in the manuals' words, must be manually reset. The JEC manuals give exactly three reset methods: cycle the line voltage to the unit; cycle 24 VAC to the ICC (remove the R or C connection); or push the TEST button down for one second and release — the manuals call the TEST button the preferred method, and warn that the ICC will attempt to start the unit when TEST is pressed. Resetting an L-code without repairing its cause does not buy a reprieve: the same protection simply counts its trips again and re-locks, and on the start-circuit lockouts each re-lock is preceded by more failed starts the lockout existed to prevent. Code 05 (open circuit) is the partial exception — it retries on its own, every five minutes for four attempts and then every twenty minutes for up to four hours. The variable-speed control follows the same philosophy through power cycling, holding its pressure lockouts (flashing 21L/29L) until the cause is corrected and power is cycled.
How to diagnose any Rheem air conditioner code
Work the problem in this order — and stop where refrigerant, compressors or mains wiring begin, because those are licensed work: (1) record the code exactly as displayed, including whether it came from the indoor display, the wired/wireless remote check mode, or an LED pattern on the outdoor unit — the three are different reports; (2) check the homeowner basics first: the air filter (a matted filter ices coils and imitates sensor and refrigerant faults), the condensate drain and float switch, the outdoor coil clear of leaves and debris, and both breakers fully on; (3) power-cycle once at the breaker, then run the mode the code interrupted and watch the sequence — indoor fan, outdoor fan, compressor start — because the stage that never starts names the fault family; (4) on mini-splits, retrieve the stored check code with the remote's diagnosis function before clearing anything, and write down the full code including its letter family; (5) a code that returns in the same mode is an active fault. Refrigerant charge, sealed-system and board-level work is professional work — an undercharged system re-iced after a reset is being damaged, not cured.
One outdoor control, three generations of Rheem air conditioner — and only two of them speak in codes
Every Rheem air-conditioner code on the internet traces back to a single component: the ICC, Rheem's Integrated Compressor Control, and its dual 7-segment display in the outdoor unit. But the ICC has shipped in two distinct generations, and Rheem's best-selling condensers have shipped without it at all — so the first diagnostic act is not reading the code but naming the generation. Generation one is the two-stage communicating line headed by the RASL-JEC (Prestige, Comfort Control2 System): a two-stage scroll compressor whose ICC shows status letters (0 standby, lower-case c for first-stage cooling, upper-case C for second-stage, t for test mode), a small set of numbered faults (01 long run time, 02 high side fault, 03 short cycling, 05/06/07 for the compressor circuits, 09 low secondary volts, 21/29 for the pressure controls, 30 for its own 3-amp fuse, 80 for low airflow, 83/84 for its two outdoor sensors, 93 for an internal control fault), the L-prefixed Active Protection lockouts, and the d-family of shared-data codes (d1, d3, d4, d8) that report on the memory card every communicating Rheem control carries. Generation two is the variable-speed EcoNet line (RA20 class): its ICC kept the same display language and the shared core of the chart — 0, c, C, 09, 21, 27, 28, 29, 83, 84, 93, d1 — rewrote the pressure lockouts as flashing 21L and 29L, and added an inverter layer underneath (L8, L15-L18, L32, L36, L42, 31) whose codes the air-conditioner documentation in this pass could not cross-verify, so they are named in the short module's unverified list rather than defined. Generation three is the absence: the Classic RA13/RA14/RA16 condensers are contactor-controlled units with pressure switches and no display, and their installation instructions publish no code table at all. A 'code' reported from such a unit is coming from somewhere else — an indoor control, a thermostat, or a website that pasted the ICC chart onto the wrong product line. Match the chart to the control before matching the code to the chart, and half the contradictions in Rheem code lists dissolve.
The same box cools and heats: why the Rheem AC chart shares codes with the heat-pump chart — and where they split
Owners comparing this page with the Rheem heat-pump hub will notice the two tables are near-twins, and that is documentation, not sloppiness: Rheem built the two-stage communicating air conditioner (RASL-JEC) and heat pump (RARL-JEC) on the same ICC, published their manuals as siblings, and printed the same diagnostic chart in both — same display, same numbering, same Active Protection arithmetic (three pressure-control trips in one call to lock out, four failed starts to lock the start and run circuits, four protector trips averaging under fifteen seconds for a locked-rotor lockout). The variable-speed generation kept the arrangement: the (-)P20 heat-pump manual's ICC chart is the chart the RA20 air conditioner reads from. So the shared codes genuinely are shared, and an AC owner can read a heat-pump manual's ICC section without being misled — with three precise exceptions. First, the displays an air conditioner can never produce: lower-case h and upper-case H (first- and second-stage heat pump operation) and d (defrost active) describe a reversing valve and a defrost cycle that a cooling-only condenser does not have; when third-party 'Rheem AC error code' lists include a defrost entry, they have copied the heat-pump chart whole. Second, the mode split inside the shared pressure codes: the chart's cause lists are written for both machines, so a 21 or 29 on an air conditioner uses only its cooling branches (frozen indoor coil, dirty filter, dead outdoor fan, dirty outdoor coil) — the heating branches (frozen outdoor coil, indoor blower in heating mode) belong to the heat pump's winter. Third, the furnace codes are a different universe entirely: Rheem's gas furnaces share the 7-segment idea and a few numbers (93 is an internal control fault on both, d1 is missing model data on both) but their 11/13/14 ignition family, 55/57 pressure-switch family and 58/59 water-sense family describe combustion events no air conditioner can have. Quote the appliance with the code — '29 on an RASL' is a diagnosis; '29 on a Rheem' is three different machines arguing.
Ruud is the same air conditioner: shared ICC, shared chart, and the EcoNet alert path on top
As with Rheem's furnaces, the Ruud air conditioner on a neighbour's pad is this air conditioner under a second badge. The JEC manuals are written for a placeholder model — '(-)ASL-JEC' — precisely because the same book covers both brands' versions of the series, with the brand letter filled in on the model number (Rheem's R, Ruud's U: RASL beside UASL), and the variable-speed documentation follows the same convention (the (-)P20 manual serves the platform both badges sell, and Rheem's own training portal is mirrored at MyRuud). Nothing in the diagnostic system is badge-specific: the same ICC, the same dual 7-segment display, the same chart from 0 through d8, the same L-terminal flash digest for conventionally wired systems, the same TEST/SW2 fault recall, and the same memory-card discipline (a card from a different unit should never be used, on either badge). A Ruud owner can therefore work from the Rheem chart on this page, and a Rheem owner from a Ruud manual, provided the generation matches — JEC chart to JEC unit, variable-speed chart to variable-speed unit. The one reporting layer that sits on top of the shared chart is the communicating wall control. On the JEC generation that was the Comfort Control2 System, which carried the fault history and the 'Call for Service' alert to the thermostat; on the variable-speed generation it is EcoNet, which re-expresses the outdoor display's events as its own A/T alert numbers at the control centre (the (-)P20 manual pairs them in its chart: under-voltage 27 with A907, over-voltage 28 with A906, high-pressure 29 with T923 and its lockout with A923, ambient-sensor 84 with T952, configuration-restore 93 with A950). Two consequences follow for owners. A communicating thermostat that shows an alert number is not contradicting the outdoor display — it is translating it, and the pair should be quoted together. And a conventionally wired system shows the homeowner nothing at all beyond an optional L-terminal flash digest, so 'the thermostat never said anything' carries no information about whether the outdoor unit has been logging faults — the display and its fault recall hold the record, on Rheem and Ruud alike.
Less common and model-specific codes
Search data shows owners also meet these codes on Rheem air conditioners: 31, 90, L15, L16, L17, L18, L32, L36, L42, L8. They are not part of the core code list Rheem publishes for most models — several are series-specific, abbreviated display readings, or codes carried over from a sister platform — so we do not publish meanings for them rather than guess. Treat them by symptom: note what the machine was doing when the code appeared (filling, draining, heating, spinning), run one full power cycle (5 minutes off), and if the code returns, match the symptom to the closest documented family in the table above and check the tech sheet stored inside your machine for the model-specific definition.
Related guides
Facts on this page were checked against manufacturer documentation: resource.gemaire.com · www.manualowl.com · pts.myrheem.com · pts.myrheem.com