Carrier Air Conditioner Error Codes List: Every Code Explained
Every Carrier air conditioner error code we could verify against Carrier'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 Carrier air conditioners
Read the amber STATUS LED on the outdoor control board: short flashes (0.25 s) are the first digit, long flashes (1 s) the second — 3 short + 2 long = 32, Carrier's own worked example. Status Code Recall Mode (short the 'force defrost' J2 pins until the green LED starts flashing, then release) replays the last 10 faults; a solid green LED means codes are stored, and ten 1-second flashes of the amber LED clears them. With a communicating Infinity control fitted, faults also appear in the control's history; variable-speed 'local' faults appear ONLY on the amber LED — they are not displayed on a generic wall control and are not recorded. On ductless systems the indoor display shows the code directly, and the indoor RUN/TIMER lamp flash pattern is a second, code-independent channel (the same flash count covers a family of codes — read the display, not just the lamps).
The complete Carrier air conditioner error code list
| Code | Meaning | Most likely cause | First fix |
|---|---|---|---|
| 1 flash, pause | Infinity outdoor control, operation indication (not a fault): low-stage cooling is running (green operation LED; on variable-speed units the same single flash shows variable-capacity mode or 2-stage LOW capacity) | Normal operation — the unit is answering a low-stage / reduced-capacity cooling demand | No repair needed. Faults are reported separately as two-digit codes on the amber status LED |
| 2 flashes, pause | Infinity outdoor control, operation indication (not a fault): high-stage cooling is running (on variable-speed units, 2-stage HIGH capacity) | Normal operation — the unit is answering a high-stage cooling demand | No repair needed |
| 16 | Infinity outdoor control (two-stage and variable-speed generations): system communications failure — communication with the user interface (Infinity wall control) has been lost | A break, short or miswiring in the ABCD communicating wiring between the user interface, the indoor unit and the outdoor unit (on variable-speed units the green LED is off when communication is lost) | Communicating-bus wiring diagnosis is technician work; correcting the wiring fault clears the code. Do not swap ABCD wires by trial |
| 25 | Infinity outdoor control (both generations; variable-speed table: 'Invalid Model Plug / Inverter Size'): the control does not detect a model plug, or detects an invalid one; the unit will not operate without the correct model plug | Model plug missing, loose, or the wrong plug fitted after a control change (on variable-speed units a replacement AOC board also ships with no model data until the plug is transferred) | A technician fits/transfers the correct model plug for the exact model — the plug carries the unit's identity and capacity data |
| 31 | Infinity outdoor control (both generations): high pressure switch open — a high-pressure switch trip has stopped the compressor. Two-stage control sequence: contactor off, outdoor fan runs up to 15 minutes, restart attempted every 15 minutes. Variable-speed units retry after a minimum 6 minutes at a reduced stage | High refrigerant pressure in cooling: check refrigerant charge, outdoor fan operation, and the outdoor coil for airflow restrictions (Carrier's stated checks in both manuals) | Clear coil/airflow restrictions and confirm the outdoor fan runs; charge and pressure-switch work is certified-technician work. Repeated trips escalate to code 84 lockout |
| 32 | Infinity outdoor control (both generations): low pressure switch open / low pressure trip — a low-pressure trip has stopped the compressor (same retry sequence as code 31; the manuals' own worked flash example — 3 short, 2 long — is this code) | Low refrigerant charge or restricted indoor airflow are Carrier's stated checks (a frozen indoor coil from a clogged filter is the classic cooling-season cause) | Check the indoor filter and airflow first; charge measurement and leak repair are certified-technician work. Repeated trips escalate to code 83 lockout |
| 33 | Infinity variable-speed outdoor control (24VNA9 table): lost inverter communications — a local fault shown on the amber LED only (not displayed on a generic wall control and not recorded in fault history); the unit retries after 6 minutes | Lost communication between the outdoor control and the compressor drive (inverter) inside the same unit | Drive/control communication diagnosis is technician work; intermittent 33s after power events that do not recur can clear on the retry |
| 45 | Infinity two-stage outdoor control: control fault — the outdoor unit control board has failed (the variable-speed generation reports its drive faults under its own 33/48/49/69/79 codes instead) | Internal failure of the outdoor control board | Control board replacement is technician work; Carrier's table gives no field repair for 45 |
| 46 | Infinity outdoor control (both generations; variable-speed table: 'Brownout Event'): brown out — line voltage fell below 187 V for at least 4 seconds; compressor and fan operation is not allowed until voltage rises above 190 V | A sagging supply: utility brownout, a failing disconnect/contactor, or undersized/damaged supply wiring dropping voltage under load | Verify line voltage at the unit. A one-off utility sag clears itself; a recurring 46 is electrician/technician work — do not keep restarting the compressor into low voltage |
| 47 | Infinity two-stage outdoor control: no 230 V at unit — there is no 230 V at the contactor while the indoor unit is powered and a cooling demand exists | Outdoor disconnect open or pulled, a tripped breaker/fuse, or broken 230 V wiring to the outdoor unit | Verify the disconnect is closed and 230 V wiring is connected (Carrier's stated action). Anything beyond the disconnect check is electrician/technician work |
| 48 | Infinity variable-speed outdoor control (24VNA9 table): lost inverter communications — the same drive-communication failure as code 33, but classified a system malfunction and therefore recorded and displayed (codes 33 and 48 are a local/system pair, not a typo) | Lost communication between the outdoor control and the inverter drive | Technician diagnosis of the drive/control link; a persistent 48 means the drive path needs repair, not another reset |
| 49 | Infinity variable-speed outdoor control: compressor over current fault — the inverter saw compressor current above its limit (local fault, amber LED only, 6-minute retry; the lockout form is code 95) | A compressor drawing excess current: failing compressor, low supply voltage under load, or a drive fault | Technician work: compressor current, supply voltage under load and drive diagnosis. Repeated over-current events escalate to the 95 lockout |
| 53 | Infinity outdoor control (both generations): outdoor air temperature (OAT) sensor fault — the sensor is not reading or is out of range | An open or shorted thermistor, or damaged sensor wiring | A technician ohms out the sensor and repairs wiring or replaces the sensor; correcting the fault clears the code |
| 54 | Infinity variable-speed outdoor control: suction temperature sensor fault — the suction thermistor is not reading correctly (this sensor pinpoints refrigerant superheat on the Infinity VS platform) | An open or shorted suction thermistor or its wiring, or a loose mounting clamp on the suction tube | A technician ohms out, reseats or replaces the sensor; the manual's own check begins with the securing clamp |
| 55 | Infinity outdoor control (both generations): outdoor coil temperature (OCT) sensor fault — the coil sensor is not reading or is out of range | An open or shorted coil thermistor or its wiring, or a sensor no longer secured tight on the coil distributor tube | A technician ohms out and reseats or replaces the sensor |
| 56 | Infinity outdoor control (both generations): thermistors out of range — an improper relationship between the coil sensor and the outdoor air sensor readings (in cooling, OAT reading 10°F or more warmer, or 25°F or more cooler, than the coil sensor on variable-speed units) | One of the two thermistors is drifting or misplaced, so the two readings no longer agree with each other | A technician ohms out both sensors and checks wiring and placement. The comparison is not performed during low-ambient cooling |
| 57 | Infinity variable-speed outdoor control: suction pressure sensor fault — the low-side pressure transducer is not reading correctly | A failed pressure transducer or its wiring (the same sensor drives the platform's low-pressure protection logic) | Transducer and wiring diagnosis is technician work; a sensor stuck at 0 psig also produces low-pressure trips |
| 59 | Infinity variable-speed outdoor control: discharge temperature out of range event — the compressor discharge temperature ran outside its allowed band; operation is limited for 15 minutes | Excess discharge temperature in cooling: low charge, a restriction, high compression ratio from a dirty outdoor coil, or a failing discharge sensor | Clean the outdoor coil and restore airflow, then a technician checks charge and the sensor. Escalation is the code 74 discharge lockout (VS-74) |
| 61 | Infinity variable-speed outdoor control: fan inverter fault — the outdoor fan's drive reported a fault (local fault, 6-minute retry; the lockout form is code 76) | A fan-drive (inverter) fault, or a fan motor fault reported through the drive | Technician diagnosis of the fan drive and motor; a fan that cannot run will take the unit down on high pressure next |
| 63 | Infinity variable-speed outdoor control: fan inverter current fault — the fan drive saw excess motor current (local fault, 6-minute retry; the lockout form is code 86) | A binding or failing fan motor, blade obstruction (debris, ice), or a drive fault | Clear any blade obstruction with the power OFF; motor/drive diagnosis is technician work |
| 65 | Infinity variable-speed outdoor control: DC voltage low — SPD limiting; the drive limited output because DC bus voltage was low (a surge protective device clamping a line event can produce this) | A supply-voltage sag seen by the inverter's DC bus, or a surge device repeatedly clamping | If it follows storms/outages and clears, monitor; recurring 65 is electrician/technician work on the supply and surge device |
| 66 | Infinity variable-speed outdoor control: outdoor fan dropped out — the fan stopped while it should have been running (an event, 6-minute timer) | A fan motor or drive dropout, or an intermittent fan power connection | Technician diagnosis if it recurs; a dropped fan quickly becomes a code 31 high-pressure trip |
| 67 | Infinity variable-speed outdoor control: stator heater fault — the compressor's stator (crankcase) heater circuit reported a fault (an event) | An open stator heater or its wiring — the heater keeps refrigerant from migrating into the oil during off cycles | Technician repair of the heater circuit; leaving it risks refrigerant migration and hard starting |
| 68 | Infinity variable-speed outdoor control: 10-minute stage 2 warmup delay — an operating event, not a failure: the platform is holding a warmup delay before allowing full stage-2 capacity | Normal platform behaviour after certain starts/conditions | No repair. Wait out the 10-minute delay; capability returns automatically |
| 69 | Infinity variable-speed outdoor control: inverter/compressor internal fault — a system malfunction inside the drive or compressor (15-minute minimum reset) | An internal fault reported by the inverter drive or the compressor it drives — Carrier's variable-speed table gives no field sub-cause | Technician drive/compressor diagnosis. A repeated 69 is a repair decision, not a reset decision |
| 71 | Infinity TWO-STAGE outdoor control only: low-stage thermal cutout — compressor operation was detected, then disappeared while low-stage demand still existed (for the variable-speed meaning of 71 see VS-71) | An internal compressor overload trip, or a start relay/capacitor held in circuit too long (if installed) | Compressor overload and start-component diagnosis is technician work. Three consecutive cycles with a thermal cutout escalate to the code 81 lockout |
| 72 | Infinity TWO-STAGE outdoor control only: high-stage thermal cutout — compressor operation was detected, then disappeared while high-stage demand still existed (variable-speed 72 is a different event — see VS-72) | An internal compressor overload trip, or a start relay/capacitor held in circuit too long (if installed) | Technician work, as for code 71. Three consecutive cycles escalate to the code 82 lockout |
| 73 | Infinity two-stage outdoor control: contactor shorted — compressor voltage is sensed when there is no demand for compressor operation | A contactor stuck (welded) closed, or a wiring error feeding the compressor | A compressor that can be powered with no call is a safety problem: switch the unit off at the disconnect and call a technician — contactor replacement is not owner work |
| 74 | Infinity two-stage outdoor control (24ANA table marks it 24ANA1 only): no 230 V at compressor — compressor voltage is not sensed when the compressor should be starting (variable-speed 74 is a different fault — see VS-74) | A contactor stuck open, or a wiring error between the contactor and the compressor | Technician work: contactor and compressor-circuit diagnosis with the cabinet open |
| 75 | Infinity two-stage outdoor control, 24ANA7 models only: low-stage did not start — the specified start voltage at the VR terminal was not achieved in low stage and the start relay was de-energised after 1 second (variable-speed 75 is unrelated — see VS-75) | A compressor that failed to start on low stage: start relay/capacitor circuit or compressor fault | Technician work: start-component and compressor diagnosis. Three consecutive failed starts escalate to code 76 |
| 76 | Infinity two-stage outdoor control, 24ANA7 models only: low-stage did not start 3 times — for 3 consecutive low-stage starts the start voltage was not achieved; low stage is locked out for 30 minutes (variable-speed 76 is unrelated — see VS-76) | The code 75 failure repeated three starts running | Do not keep cycling it: the failed-start cause (start relay, capacitor, compressor) needs a technician's diagnosis |
| 77 | Infinity two-stage outdoor control, 24ANA7 models only: high-stage did not start — the specified start voltage at the VS terminal was not achieved in high stage and the start relay was de-energised after 1 second (variable-speed 77 is unrelated — see VS-77) | A compressor that failed to start on high stage: start relay/capacitor circuit or compressor fault | Technician work, as for code 75. Three consecutive failed starts escalate to code 78 |
| 78 | Infinity two-stage outdoor control, 24ANA7 models only: high-stage did not start 3 times — for 3 consecutive high-stage starts the start voltage was not achieved; high stage is locked out for 30 minutes | The code 77 failure repeated three starts running | Technician diagnosis of the start circuit and compressor before the stage is run again |
| 81 | Infinity two-stage outdoor control: low-stage thermal lockout — a thermal cutout has occurred in three consecutive cycles; low stage is locked out for 4 hours or until 24 V power is recycled | Whatever caused the repeated code 71 cutouts: a compressor repeatedly tripping its internal overload, or start components held in circuit | Do not just recycle power and re-lock it: the repeated overload trips need a technician's compressor diagnosis before the stage is run again |
| 82 | Infinity TWO-STAGE outdoor control only: high-stage thermal lockout — a thermal cutout has occurred in three consecutive cycles; high stage is locked out for 4 hours or until 24 V power is recycled (variable-speed 82 is a different lockout — see VS-82) | The code 72 family, repeated: internal overload trips or start-component faults on high stage | Technician compressor diagnosis, as for code 81 |
| 83 | Infinity outdoor control (both generations): low pressure lockout — a low pressure switch trip has occurred during three consecutive cycles; unit operation is locked out for 4 hours or until 24 V power is recycled | The code 32 family repeated three cycles running: low charge, a restriction, or indoor airflow too low (a coil frozen by a clogged filter) | Fix the 32 cause first (filter/airflow, then certified charge and leak work). Recycling power without the repair just re-enters the lockout count |
| 84 | Infinity outdoor control (both generations): high pressure lockout — a high pressure switch trip has occurred during three consecutive cycles; unit operation is locked out for 4 hours or until 24 V power is recycled | The code 31 family repeated three cycles running: dirty/restricted outdoor coil, outdoor fan not moving air, or overcharge | Clean the outdoor coil and confirm fan operation, then a technician verifies charge and the switch. Do not defeat the lockout — it is the compressor's last protection |
| 85 | Infinity two-stage outdoor control, 24ANA7 models only: low contactor open — compressor voltage is not sensed when the compressor should be starting; the low-stage contactor may be stuck open or there is a wiring error | A contactor stuck open, or a wiring error in the low-stage compressor circuit | Technician work: contactor and compressor-circuit diagnosis |
| 87 | Infinity two-stage outdoor control, 24ANA7 models only: high contactor open — compressor voltage is not sensed when the compressor should be starting; the high-stage contactor may be stuck open or there is a wiring error | A contactor stuck open, or a wiring error in the high-stage compressor circuit | Technician work, as for code 85 |
| 91 | Infinity variable-speed outdoor control: inverter VDC-out over voltage event — the drive's DC output voltage went high (a local event, 6-minute timer; the lockout form is code 97) | A supply surge or a drive voltage-regulation fault | Events after storms that clear can be monitored; recurring 91/97 is drive and supply diagnosis by a technician |
| 92 | Infinity variable-speed outdoor control: inverter VDC-out under voltage event — the drive's DC output voltage sagged (a local event, 6-minute timer; the lockout form is code 96) | A supply sag reaching the drive, or a drive power-stage fault | Verify supply voltage under load; recurring events are technician/electrician work |
| 95 | Infinity variable-speed outdoor control: compressor over current lockout — the code 49 fault escalated; locked out for 2 hours as a system malfunction | A compressor repeatedly over current: mechanical failure, low voltage under load, or drive fault | Compressor and drive diagnosis before restart — a compressor locked out on current is telling you it is failing or starved of voltage |
| 96 | Infinity variable-speed outdoor control: VDC under voltage lockout — the code 92 condition escalated; locked out for 2 hours as a system malfunction | Persistent low DC voltage at the drive: supply problem or drive power-stage failure | Electrician/technician supply and drive diagnosis |
| 97 | Infinity variable-speed outdoor control: VDC over voltage lockout — the code 91 condition escalated; locked out for 2 hours as a system malfunction | Persistent high DC voltage at the drive: supply surge damage or drive regulation failure | Drive and supply diagnosis; check surge protection after storm-related lockouts |
| 98 | Infinity variable-speed outdoor control: high torque event — the compressor demanded torque above the drive's normal band (an event, not yet a lockout) | A compressor working against abnormal load: liquid slugging, very high head pressure, or early mechanical failure | Technician diagnosis if it recurs — high torque is an early warning; the lockout form is code 99 |
| 99 | Infinity variable-speed outdoor control: high torque lockout — repeated high-torque events; locked out for 2 hours as a system malfunction | The code 98 condition persisted: a compressor under damaging mechanical or refrigerant load | Do not cycle power to defeat the 2-hour lockout. Compressor and refrigerant-circuit diagnosis is required before restart |
| -- (mode conflict) | Carrier ductless (current code system): mode conflict — on a multi-zone system one indoor unit is calling for heating while another calls for cooling; the display shows '- -' with the operation lamp on steady and the timer lamp flashing once per cycle | Mixed-mode demand the outdoor unit cannot satisfy (a platform behaviour of multi-zone systems, not a broken part) | Set all indoor units to the same mode family (all cooling or all heating). No repair is needed |
| EC07 | Carrier ductless (current code system): the outdoor fan speed has been operating outside its normal range (operation lamp flashes 12 times per cycle) | A stalled, obstructed or failed outdoor fan motor, or the fan feedback circuit on the outdoor board | Clear obstructions with power off; motor and board diagnosis is technician work |
| EC51 | Carrier ductless (current code system): outdoor unit EEPROM parameter error (operation lamp flashes 5 times per cycle with the timer lamp off; on the legacy outdoor display the same board fault shows as E5) | The outdoor control board's parameter memory has failed | Outdoor PCB replacement is technician work |
| EC52 | Carrier ductless (current code system): T3 sensor open circuit or short circuit — T3 is the outdoor coil temperature sensor (operation lamp flashes 5 times per cycle) | An open/shorted outdoor coil thermistor or its wiring | A technician ohms out the T3 sensor and repairs wiring or replaces the sensor |
| EC53 | Carrier ductless (current code system): T4 sensor open circuit or short circuit — T4 is the outdoor ambient temperature sensor (operation lamp flashes 5 times per cycle) | An open/shorted outdoor ambient thermistor or its wiring | A technician ohms out and repairs or replaces the T4 sensor |
| EC54 | Carrier ductless (current code system): TP sensor open circuit or short circuit — TP is the compressor discharge temperature sensor (operation lamp flashes 5 times per cycle) | An open/shorted discharge thermistor or its wiring | A technician ohms out and repairs or replaces the TP sensor — the manual's seating position for TP is on the discharge pipe at the compressor |
| EC56 | Carrier ductless (current code system): T2B sensor open circuit or short circuit — T2B is the evaporator outlet temperature sensor fitted on multi-zone systems (operation lamp flashes 5 times per cycle) | An open/shorted T2B thermistor or its wiring on a multi-zone indoor unit | A technician ohms out and repairs or replaces the T2B sensor |
| EH00 | Carrier ductless (current code system, 40MAHB family): indoor unit EEPROM parameter error — shown on the indoor display with the operation lamp flashing once per cycle | The indoor control board's parameter memory has failed or been corrupted | Service-manual diagnosis starts at the indoor PCB: a board that cannot hold its parameters is replaced. This is ductless-only — ducted Infinity boards report their faults in the two-digit system instead |
| EH0B | Carrier ductless (current code system): indoor PCB / display board communication error — the main indoor board and the display board are not communicating (manual documents render the code as EH0b; its diagnosis section heads it EH06 — same fault, two renderings) | A failed display board, a disconnected display cable, or the indoor main board's communication circuit | Cable and board diagnosis is technician work |
| EH02 | Carrier ductless (current code system): zero-crossing signal detection error (operation lamp flashes 3 times per cycle) | The indoor board cannot detect the AC supply's zero-crossing signal it uses to time the fan drive (the manual notes the diagnosis applies to units with AC fans; DC-fan models skip this step) | Indoor board diagnosis/replacement is technician work |
| EH03 | Carrier ductless (current code system): the indoor fan speed has been operating outside its normal range (operation lamp flashes 4 times per cycle) | A stalled, binding or failed indoor fan motor, a blocked blower wheel, or the fan feedback circuit on the indoor board | With power off, check the blower wheel spins freely and is clean; motor and board diagnosis is technician work |
| EH60 | Carrier ductless (current code system): T1 sensor open circuit or short circuit — T1 is the indoor room temperature sensor (operation lamp flashes 6 times per cycle) | An open/shorted room thermistor or its wiring at the indoor unit | A technician ohms out and repairs or replaces the T1 sensor |
| EH61 | Carrier ductless (current code system): T2 sensor open circuit or short circuit — T2 is the indoor coil (evaporator) temperature sensor (operation lamp flashes 6 times per cycle) | An open/shorted evaporator thermistor or its wiring | A technician ohms out and repairs or replaces the T2 sensor |
| EHB1 | Carrier ductless (current code system): indoor unit board and multi-function (module) communication error on feature-equipped models | The add-on multi-function module and the indoor board are not communicating — a loose module connection or a failed module | Technician checks the module connection and replaces the failed part |
| EL0C | Carrier ductless (current code system): refrigerant leakage detection — the system's leak-detection logic (coil temperature behaviour against run time) has tripped; the unit stops and cannot restart until power is cycled | Low refrigerant from a leak is the condition it detects; the same signature can follow a restriction or a sensor problem, so the code is a detection, not proof of a leak by itself | Certified leak search and repair, then recharge. Cycling power to restart a unit that is detecting leakage just runs a dry compressor |
| EL01 | Carrier ductless (current code system): indoor/outdoor unit communication error — the two units have stopped exchanging data (operation lamp flashes twice per cycle; the outdoor unit's own table shows the same fault at its CPU LED) | A break or miswiring in the interconnecting cable between indoor and outdoor units, a failed communication circuit on either board, or reversed signal/neutral wiring | Technician checks the interconnect cable end-to-end and both boards' communication circuits; sensor and charge work will not clear a communication error |
| FH0D | Carrier ductless (current code system): ioniser malfunction on models fitted with an ioniser (operation lamp flashes 11 times per cycle) | A failed ioniser module or its connection at the indoor unit | Module diagnosis/replacement is technician work; cooling itself is unaffected, but the fault keeps displaying until repaired |
| P0 (ductless) | Carrier ductless, LEGACY single-letter display (38/40MB generation; also how the current manual's outdoor-unit LED tables report the drive fault): IPM malfunction or IGBT over-current/short-circuit protection — the legacy form of the PC00 family. Never read ductless P0 onto ducted equipment | Inverter power module failure or compressor-drive over-current in the outdoor unit | Technician drive-board/compressor diagnosis |
| P1 (ductless) | Carrier ductless, LEGACY single-letter display: over-voltage or too-low-voltage protection — the legacy form of PC01 | Supply voltage outside the allowed band, or a DC-bus fault on the outdoor board | Verify the supply first; a healthy supply with repeating P1 means outdoor-board diagnosis |
| P2 (ductless) | Carrier ductless, LEGACY single-letter display: high temperature protection of the compressor top (the 40MB installation manual's wording; the platform presentation phrases the same code as compressor-top or IPM high-temperature protection) — the legacy form of PC02 | Compressor overheating: dirty outdoor coil, failed fan, overcharge, or low airflow over the outdoor unit | Clean the coil and confirm the fan; the rest is technician work |
| P3 (ductless) | Carrier ductless, LEGACY single-letter display: outdoor low temperature protection — a protection state for very cold outdoor ambient, listed in the 40MBF installation manual's protection table | Outdoor ambient below the platform's operating envelope (a protection, not a failed part) | No repair: operation resumes when ambient returns to range |
| P4 (ductless) | Carrier ductless, LEGACY single-letter display: inverter compressor drive error — the legacy form of PC04 (Carrier's own outdoor-unit tables in the current manual still surface this fault as P4) | Compressor drive abnormality: compressor electrical fault or drive-stage failure | Technician drive/compressor diagnosis |
| P5 (ductless) | Carrier ductless, LEGACY single-letter display: mode conflict on multi-zone systems — the legacy form of the '- -' display | Indoor units demanding heating and cooling at the same time | Align all indoor units to one mode family; no repair needed |
| P6 (ductless) | Carrier ductless, LEGACY single-letter display: compressor low pressure protection — the legacy form of the PC03 protection | Low refrigerant pressure: charge loss, restriction, or a sensing fault | Certified leak/charge diagnosis |
| P7 (ductless) | Carrier ductless, LEGACY single-letter display: outdoor IGBT temperature sensor error, listed in the 40MBF installation manual's protection table | The IGBT temperature sensor on the outdoor drive board is open/shorted or the board cannot read it | Outdoor board-level diagnosis by a technician |
| PC00 | Carrier ductless (current code system): IPM malfunction, or IGBT over-current/short-circuit protection (PC family: operation lamp flashes 7 times per cycle and the timer lamp flashes — the legacy outdoor display shows this drive fault family as P0) | A failed inverter power module (IPM) in the outdoor unit, or an over-current/short in the compressor drive output | Outdoor drive-board/compressor diagnosis is technician work — PC codes are drive-level faults, not settings |
| PC01 | Carrier ductless (current code system): over-voltage or too-low-voltage protection on the DC bus (operation lamp flashes twice per cycle, timer lamp flashing; legacy display P1) | Supply voltage outside the inverter's allowed band, or a failing DC-bus circuit on the outdoor board | Verify supply voltage at the unit first (an electrician's job if the supply is at fault); a correct supply with a repeating PC01 means outdoor-board diagnosis |
| PC02 | Carrier ductless (current code system): high temperature/pressure protection of the compressor or IPM module (operation lamp flashes 3 times per cycle, timer lamp flashing; legacy display P2) | The compressor top or the IPM heatsink ran too hot: dirty outdoor coil, failed outdoor fan, overcharge, or a heatsink compound/mounting failure | Clean the outdoor coil and confirm the fan; charge and heatsink work is technician work |
| PC03 | Carrier ductless (current code system): low pressure protection (operation lamp flashes 7 times per cycle, timer lamp flashing; the platform's code presentation lists the same protection as PC32 — the 40MAHB service table's PC03 is the form verified against the diagnosis section) | Refrigerant pressure fell below the protection threshold: charge loss/leak, a restriction, or a failed low-pressure reading | Certified leak/charge diagnosis; do not run the unit dry on repeated resets |
| PC04 | Carrier ductless (current code system): inverter compressor drive error (operation lamp flashes 5 times per cycle, timer lamp flashing; legacy display P4) | The drive could not run the compressor correctly: a compressor electrical fault, a drive-stage failure, or a wrong compressor connection after service | Technician drive/compressor diagnosis |
| PC08 | Carrier ductless (current code system): current overload protection (operation lamp flashes once per cycle, timer lamp flashing) | Input current above the protection limit: a compressor drawing hard, low supply voltage under load, or a current-sensing fault | Supply voltage under load first, then technician compressor/drive diagnosis |
| PC40 | Carrier ductless (current code system): communication error between the outdoor main chip and the compressor drive chip (operation lamp flashes 6 times per cycle, timer lamp flashing) | A failed communication path inside the outdoor unit — board-level, between the main control chip and the drive chip | Outdoor board replacement-level diagnosis; there is no wiring fix external to the unit for PC40 |
| VS-71 | Infinity VARIABLE-SPEED outdoor control: compressor dropped out — compressor operation was running, then dropped out while demand existed (an event; two-stage code 71 is a different fault — a thermal cutout — so never read one table onto the other control) | The drive shut the compressor down or lost it mid-run: a protection trip, a power dip, or a drive event logged under its own code as well | Read the full stored history (Status Code Recall Mode) — the dropout usually pairs with the protection code that caused it; that pair is the diagnosis |
| VS-72 | Infinity VARIABLE-SPEED outdoor control: suction over temperature event — suction temperature ran too hot for 15 minutes of limited operation (two-stage code 72 is a thermal cutout; a different event) | High superheat: low charge, a restriction starving the evaporator, or very low indoor airflow | Restore indoor airflow, then certified charge/restriction diagnosis. Escalation is the VS-82 suction over-temperature lockout |
| VS-74 | Infinity VARIABLE-SPEED outdoor control: discharge temperature out of range lockout — the code 59 condition escalated; locked out for 2 hours as a system malfunction (two-stage code 74 is 'no 230 V at compressor'; a different fault) | Sustained excessive discharge temperature: low charge, restriction, or a compressor being destroyed by its own heat | Locked out for 2 hours by design. Compressor discharge temperature this high needs certified diagnosis before any restart |
| VS-75 | Infinity VARIABLE-SPEED outdoor control: maximum power mode — temperature; the drive entered its maximum-power limiting mode on temperature (a local operating event, not the two-stage code 75 'did not start') | The drive protecting itself at high thermal load | Clear outdoor-coil restrictions and shading/airflow problems around the unit; recurring limiting with a clean coil is technician work |
| VS-76 | Infinity VARIABLE-SPEED outdoor control: fan inverter lockout — the code 61 fan-drive fault escalated; locked out for 2 hours as a system malfunction (two-stage code 76 is 'low-stage did not start 3 times'; unrelated) | A fan drive or motor fault that repeated past the retry limits | Fan drive/motor replacement is technician work; the unit cannot cool safely without the outdoor fan |
| VS-77 | Infinity VARIABLE-SPEED outdoor control: maximum power mode — compressor current; the drive entered maximum-power limiting on compressor current (a local operating event; two-stage code 77 is 'high-stage did not start'; unrelated) | The compressor drawing near-limit current under load — high head pressure, low voltage, or a compressor wearing out | Clean the coil, verify airflow and supply voltage; recurring current limiting needs a technician's compressor evaluation |
| VS-79 | Infinity VARIABLE-SPEED outdoor control: compressor/inverter fault — a drive-reported compressor or inverter fault (local fault, 6-minute retry; the lockout form is code 88) | The inverter drive detected a compressor-side or internal drive abnormality | Technician drive/compressor diagnosis; repeated events become the VS-88 lockout |
| VS-82 | Infinity VARIABLE-SPEED outdoor control: suction over temperature lockout — the VS-72 condition escalated; locked out for 4 hours as a system malfunction (two-stage code 82 is a high-stage thermal lockout; a different fault) | Sustained suction over-temperature: charge loss or a starving evaporator run for a long time | Certified charge and refrigeration-circuit diagnosis before restart; the 4-hour lockout protects a compressor cooking on hot suction gas |
| VS-86 | Infinity VARIABLE-SPEED outdoor control: fan inverter current lockout — the code 63 fan-current fault escalated; a system malfunction (this 'system malfunction' class has no fixed 2-hour timer in the table — see the manual; it is NOT the 'low contactor shorted' meaning third-party lists give a two-stage 86, which Carrier's two-stage tables do not contain) | A fan motor drawing excess current repeatedly: binding motor, obstruction, or drive failure | Technician fan motor/drive diagnosis; clear obstructions with power off first |
| VS-88 | Infinity VARIABLE-SPEED outdoor control: compressor/inverter lockout — the VS-79 fault escalated; locked out for 2 hours as a system malfunction | A drive/compressor fault that repeated past retry limits | Drive or compressor replacement decision by a technician — repeated restarts into a locked-out drive fault can destroy the drive |
How to reset / clear error codes on Carrier air conditioners
Pressure and thermal trips on the Infinity outdoor control retry on the control's own schedule — the two-stage manual's sequence runs the outdoor fan up to 15 minutes and attempts a restart every 15 minutes; variable-speed tables state a per-code minimum reset (commonly 6 minutes, 15 minutes for internal/discharge faults). Lockouts hold for the stated 4 hours (thermal/pressure/suction) or 2 hours (drive, discharge, torque, voltage) or until 24 V power is recycled where the table allows. Cycling low voltage defeats the 15-minute two-stage delay — the manual says so, which is exactly why power-cycling is not a diagnosis. Ductless sensor codes clear when the sensor reads normally; the ductless leak-detection trip (EL0C) will not restart until power is cycled, by design.
How to diagnose any Carrier 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 brand name, three unrelated code systems
A Carrier air conditioner can report its faults in three completely different languages, and the single most common Carrier troubleshooting error is reading a code in the wrong one. Communicating Infinity systems — the ducted condensers and heat pumps run by an Infinity wall control — report two-digit codes from an outdoor control board: flashed on an amber LED, listed in the control's fault history, and defined in the model's installation manual troubleshooting table. Carrier ductless (mini-split) systems report letter-and-number display codes — EH00, EL01, EC52, PC04 and their kin — from an entirely different platform that Carrier shares with its manufacturing partner's global mini-split line. And Carrier's non-communicating Comfort and Performance condensers publish no fault-code table at all in their installation documents: a conventional unit's silence is not a missing page, it is the design. Before any code on this page means anything, identify which of the three systems produced it. An 'E1' read off a ductless display (indoor/outdoor communication error) has nothing to do with a ducted Infinity board, which has no E-codes; a two-digit '32' flashing on an outdoor board (low pressure switch open) has nothing to do with a ductless unit, which expresses low pressure as PC03. The hub table therefore labels every row with its platform, and the platform label is part of the code's meaning — a Carrier number without its platform is only half a diagnosis, and acting on the wrong half wastes a service call or worse.
The Infinity split: two generations whose numbers collide
Even inside the Infinity family, one table is not enough, because Carrier has shipped two generations of outdoor control whose code numbers overlap while their meanings diverge. The two-stage generation (Infinity 24ANB1/24ANA and their Performance siblings) monitors pressure switches, contactors and compressor starting: its distinctive codes are starting and contactor faults — 73 contactor shorted, 75/77 'did not start', 76/78 'did not start 3 times', 85/87 contactor open on the 24ANA7 — and its 71/72 are thermal cutouts, compressor operation sensed and then lost. The variable-speed generation (24VNA9 air conditioners, 25VNA8 heat pumps) is an inverter platform, and its table is a drive engineer's table: lost inverter communications twice over (33 as a local LED-only fault, 48 as the recorded system-malfunction twin), compressor over-current (49, locking out as 95), fan inverter faults (61/63, locking out as 76/86), DC-bus voltage events (65, 91/92, locking out as 96/97), suction and discharge temperature management (54, 57, 59, VS-72, VS-74, VS-82), and high-torque protection (98, locking out as 99). Where the generations collide, the hub keys the variable-speed row 'VS-': VS-71 is 'compressor dropped out', not the two-stage thermal cutout; VS-82 is a suction over-temperature lockout, not the two-stage high-stage thermal lockout; VS-76 is a fan inverter lockout, not 'did not start 3 times'. The shared core — 16 communications, 25 model plug, 31/32 pressure trips, 46 brownout, 53/55/56 sensors, 83/84 pressure lockouts — genuinely is shared, with the same retry logic: trips retry (the two-stage sequence runs the fan up to 15 minutes and retries every 15 minutes; three trips in consecutive cycles convert a trip into a 4-hour lockout). Read the generation off the model number before reading the code off the board.
Reading Carrier codes properly: LEDs, recall mode, and lamps
On an Infinity outdoor unit the amber STATUS LED is the primary instrument. It flashes two-digit codes as short flashes (0.25 seconds) for the first digit and long flashes (1 second) for the second, with a 2.5-second pause before repeating — Carrier's own example is 3 short + 2 long for code 32, low pressure switch open. One and two steady flash patterns are not faults at all: 1 flash with a pause is low-stage operation, 2 flashes high-stage. The board also remembers: Status Code Recall Mode, entered by briefly shorting the 'force defrost' J2 connector pins, replays the last ten stored faults (useful because the code that stopped the compressor at 3 a.m. may have cleared by the time anyone looks), and a communicating Infinity control keeps its own event history where system malfunctions — but not variable-speed 'local' faults, which live and die on the LED — can be read in comfort. On ductless systems the indoor display shows the code outright, but the lamp pattern beside it is a real second channel: the operation lamp's flash count identifies the fault family and the timer lamp separates protections (timer flashing, the PC family) from errors (timer off), so 'operation flashes 5, timer off' narrows the field before the display is even read — and when the display itself has failed, the outdoor unit repeats the same families on its CPU-board LEDs, with the newest manual's outdoor tables even translating some faults back into the legacy P0/P1/P4 short forms. Two cautions close the topic. First, a fault history is evidence, not a verdict: a brownout (46) logged during a storm explains itself, while a pressure lockout (83/84) repeated across days is a compressor asking for help. Second, never 'test' a lockout by recycling power repeatedly — the manuals permit recycling to defeat a delay precisely because they assume the cause was found first.
Less common and model-specific codes
Search data shows owners also meet these codes on Carrier air conditioners: 52. They are not part of the core code list Carrier 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: mans.io · manualzilla.com · homeappliance.manualsonline.com · resource.carrierenterprise.com · archive.org · manuals.plus · site-696018.mozfiles.com