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Carrier Air Conditioner 53 / 55 / 56 Error Code
Outdoor air or coil sensor fault on Carrier air conditioners.
CarrierAll Carrier air conditioner codes
Code 53 points to the outdoor air temperature sensor and 55 to the outdoor coil sensor: the board is reading nothing from it, or a value that can't be right. Code 56 means the two readings disagree in a way that doesn't make sense, which can be one bad sensor or a wiring fault.
Compatible models
Infinity two-stage 24ANB7 and 25HNB6/25HNB9 outdoor units. Carrier's installation instructions list all three.
Also shown as
On heat pumps these sensors help decide when to defrost, so a fault can upset winter heating.
Difficulty
Try the basic checks, but the usual fix is a technician's job.
Not sure you are reading the code right? See how to read Carrier air conditioner codes.
How to fix Carrier 53 / 55 / 56
Clear the area around the unit
With the power off, rake away snow, leaves and debris from the base and sides of the outdoor unit so it can breathe and drain.
Reset once
Cycle power to the outdoor and indoor units and see whether the code returns over the next few cycles.
When to call a technician
Testing a thermistor means measuring resistance on the board's wiring inside the control box. Leave it to a technician.
Parts linked to 53 / 55 / 56
These are the parts most often behind this code. Tap one to see what it does and the signs it is failing.
Order parts by your full model number so they fit.
Frequently asked questions
Which Carrier models show the 53 / 55 / 56 code?
Infinity two-stage 24ANB7 and 25HNB6/25HNB9 outdoor units. Carrier's installation instructions list all three.
Can I fix Carrier 53 / 55 / 56 myself?
Only the basic checks. You can safely try the steps above, but 53 / 55 / 56 usually points to a part or fault that needs a technician.
Other Carrier air conditioner codes
- Solid / 1 / 2Status light showing normal operation
- 16Lost communication with the Infinity control
- 25Model plug missing or wrong
- 31 / 84High-pressure switch tripped or locked out
- 32 / 83Low-pressure or discharge temperature trip
- 45Outdoor control board fault
- 46Brown-out: supply voltage too low
- 47No 230-volt power reaching the outdoor unit
- 71 / 72 / 81 / 82Compressor thermal cutout or lockout
- 73 / 74Contactor stuck closed or not closing
- E1Ductless indoor and outdoor units not talking
- ECRefrigerant leak detected
- E3 / F5Ductless fan speed out of range
- E4 / E5 / F1 / F2 / F3Ductless temperature sensor open or shorted
- F0 / P1Ductless overcurrent or voltage protection
- P3Too cold outside to heat
- P5Multi-zone mode conflict
- CL / dFFilter reminder or defrost in progress
Last reviewed 2026-10-22. Codes and steps can vary by model; check your owner's manual.