Home › Carrier › Air Conditioners › E4 / E5 / F1 / F2 / F3
Carrier Air Conditioner E4 / E5 / F1 / F2 / F3 Error Code
Ductless temperature sensor open or shorted on Carrier air conditioners.
CarrierAll Carrier air conditioner codes
One of the system's thermistors is reading open or shorted. E4 is the room air sensor and E5 the indoor coil sensor; F1, F2 and F3 are the outdoor air, outdoor coil and compressor discharge sensors. Carrier names the sensor, its wiring or the board.
Compatible models
Carrier 40MAQ and 40MHH high-wall ductless units, per their service manuals.
Also shown as
With just one sensor down, the unit can keep running while it shows the code. If more than one fails, it stops.
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 E4 / E5 / F1 / F2 / F3
Reset the power
Turn the system off at the breaker for several minutes and back on. A code caused by a glitch should stay gone.
Note which code it is
Write down whether it starts with E (indoor) or F (outdoor). That tells the technician which unit to open.
When to call a technician
Sensors are wired to the boards inside the indoor and outdoor units, so a code that comes back after a reset is a service call.
Parts linked to E4 / E5 / F1 / F2 / F3
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 E4 / E5 / F1 / F2 / F3 code?
Carrier 40MAQ and 40MHH high-wall ductless units, per their service manuals.
Can I fix Carrier E4 / E5 / F1 / F2 / F3 myself?
Only the basic checks. You can safely try the steps above, but E4 / E5 / F1 / F2 / F3 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
- 53 / 55 / 56Outdoor air or coil sensor fault
- 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
- 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.