The first thing worth knowing is that the Infinity touchscreen has no fault code list of its own. The control is a messenger — it displays whatever number the furnace, air handler or outdoor unit reports to it, and stores the recent ones in a Run/Fault History screen with a last-ten-faults reset. That history is the screen worth checking first, because it catches trips that happened overnight and cleared themselves before you noticed.
The same number is also flashed by the amber STATUS LED on the outdoor control board, which is how a technician reads a unit that is not communicating. Carrier's own service manuals sort these numbers into events, local faults and system malfunctions: an event is logged and ridden out, a local fault stages the compressor down, and a system malfunction locks the unit out — often for two or four hours, which is why a unit that quit at noon sometimes restarts by itself at four.
Codes vary by model, and on Carrier they vary more than most: the variable-speed Greenspeed units and the older two-stage Infinity units use overlapping numbers with different meanings. Code 45 is a compressor winding fault on a variable-speed unit and a control fault on a two-stage one. Let the legend inside your own access panel win over any list, this one included. Carrier furnace faults are on the Carrier furnace error code guide, lines and warranty terms on the Carrier repair page, and cooling work generally under air conditioner service.
Carrier AC & heat pump codes, decoded
| Code | What it means | Safe? | Try first | When to call |
|---|---|---|---|---|
16 | Communication loss between the outdoor unit and the rest of the system. | keep running | Look for obvious damage to the low-voltage cable where it leaves the house. | Call — bus faults are usually a chewed wire, a loose terminal or a failed board. |
25 | Invalid model plug or inverter size mismatch. | turn it off | Nothing to try. This almost always follows recent service or a board swap. | Call whoever last opened the unit. The plug configures the board to the equipment. |
31 | High pressure switch open — the unit stages itself down each time it happens. | turn it off | Turn it off, then clear anything crowding the outdoor coil: a fence, a deck box, cottonwood. | Call if the coil is clean — the condenser fan and the charge are next on the list. |
32 | Low pressure trip. Three occurrences in a row elevate it to lockout code 83. | turn it off | Shut it down. Check for ice on the copper lines and oily residue at the service valves. | Call. Refrigerant is not consumed, so a low-pressure trip means it went somewhere. |
45 | Compressor winding fault on variable-speed units. On two-stage Infinity units the same number means a control fault. | turn it off | One breaker cycle is a fair test. If 45 returns, leave the system off. | Call — and tell us your model, because this number means two different things. |
46 | Brownout event — incoming line voltage dropped below the control's limit. | turn it off | Check whether the house lights dipped too. It clears once voltage recovers. | Call if 46 keeps returning on a calm day — that is a supply or connection problem. |
48 | Lost inverter communications, elevated to a lockout after repeated occurrences. | turn it off | No homeowner fix. Leave the system off rather than forcing restarts. | Call. The control and the inverter drive have stopped talking to each other. |
53 | Outdoor air temperature sensor fault. | keep running | Nothing safe to do inside the cabinet. Note any odd staging or defrost behaviour. | Book it before winter — a heat pump without this reading defrosts on guesswork. |
55 | Outdoor coil temperature sensor fault. | keep running | Clear leaves and grass clippings off the coil so the reading it gets is honest. | Call ahead of heating season; defrost timing depends on this sensor. |
56 | Outdoor air and coil thermistors reading out of range relative to each other. | keep running | No action available to you. The unit is flagging two readings that disagree. | Book a visit — one of the two sensors is drifting and both get measured. |
57 | Suction pressure sensor fault on variable-speed units. | turn it off | Power the system down rather than letting it keep modulating blind. | Call. The drive uses this reading to decide how hard to run the compressor. |
62 | Compressor no start — the unit commanded a start and nothing happened. | turn it off | Confirm the outdoor disconnect is on and the breaker has not tripped. | Call if power is present. Repeated start attempts are hard on a stalled compressor. |
69 | Inverter or compressor internal fault. | turn it off | Leave it off. Do not keep resetting to see whether it holds this time. | Call the same day — this is the code that decides repair against replacement. |
83 | Low pressure lockout — the unit is locked out for four hours. | turn it off | Do not wait for the four hours to pass and call it fixed. It will trip again. | Call. A repeated low-pressure lockout is a leak until proven otherwise. |
84 | High pressure lockout for four hours, elevated from repeated 31 trips. | turn it off | Turn it off and check the outdoor coil and the space around the cabinet. | Call — airflow, a failing fan or an overcharge, in that order of likelihood. |
95 | Compressor over-current lockout, elevated after repeated over-current faults. | turn it off | Leave the system off between attempts rather than cycling the breaker. | Call the same day. Each forced restart takes life off the compressor. |
179 | Loss of communication with the outdoor AOC board, reported at the user interface. | turn it off | Nothing to try beyond one power cycle. | Call. Carrier's own literature points at the AOC board or the inverter here. |
The codes that usually mean a real repair
32 and 83 — the low-pressure trip that becomes a lockout
These are the same fault at two stages of seriousness: 32 is the trip, and three of them in a row become an 83 lockout. Homeowners want this to be a top-up, and it almost never is — a sealed system that has lost pressure has a leak, at a service valve, a braze joint or the evaporator. Finding it, sealing it and recharging by weight typically lands at $300–$800. Newer Carrier condensers ship with R-454B rather than R-410A, which changes handling and cost; the A2L refrigerant guide explains what that means for a repair.
31 and 84 — high head pressure, usually airflow
Roughly half the high-pressure trips we attend are not electronic at all. A coil furred with cottonwood, a garden bed grown tight against the cabinet, deck storage stacked beside it, or a condenser fan that has slowed will all drive head pressure up until the switch opens. A run capacitor is the cheap end at $150–$350; a condenser fan motor is $300–$700 fitted. Only when the coil is genuinely clean and the fan is strong do we start measuring the charge.
48, 69 and 179 — the inverter drive
This group is where a Carrier repair conversation gets expensive, because the inverter drive and the compressor are the two costliest parts in the outdoor unit. Carrier's service literature points these at the AOC board or the inverter itself, and on a variable-speed unit past a decade the arithmetic often favours replacement. We measure before recommending, and the diagnostic visit is $90–$150, credited to the repair if you proceed.
Licensed technicians, trucks stocked with Carrier parts, no overtime charges.
Common questions
Is there a separate list of Infinity System Control fault codes?
No, and that is worth knowing before you go looking. The Infinity touchscreen does not generate its own codes — it displays whatever the furnace, air handler or outdoor unit reports and keeps them in a Run/Fault History screen. Any page offering a dedicated code list for the control itself is inventing one.
Why did my Carrier unit start working again on its own?
Because most Carrier system malfunctions are timed lockouts rather than permanent stops. Low and high pressure lockouts hold the unit for four hours; several of the inverter and voltage lockouts hold it for two. A unit that quit at noon and restarted at four has not repaired itself — it has waited out a timer, and the fault is still there.
What is the difference between a Carrier event, a fault and a system malfunction?
An event is logged and ridden out, so you may never notice it. A local fault stages the compressor down to protect it and often elevates to a lockout if it repeats. A system malfunction stops the unit. That ladder is why Carrier numbers come in pairs — 32 elevates to 83, 31 elevates to 84, and repeated compressor over-current faults elevate to 95.
My Carrier condenser has no display, only a flashing light. What now?
Count the flashes. The amber STATUS LED on the outdoor control board flashes the same number the control would display, and Carrier prints the legend on the wiring diagram inside the access panel — a compartment carrying live 240-volt terminals, so it is not a homeowner job. Count what you can see through the louvres and book a technician.
Does the same code mean the same thing on every Carrier outdoor unit?
No. Variable-speed Greenspeed units and older two-stage Infinity units share numbers with different meanings — 45 is the clearest example, meaning a compressor winding fault on one and a control fault on the other. Give us the model number off the rating plate along with the code, because the number alone is genuinely ambiguous on this brand.