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Carrier Air Conditioner 73 / 74 Error Code
Contactor stuck closed or not closing on Carrier air conditioners.
CarrierAll Carrier air conditioner codes
Code 73 means the board senses voltage at the compressor when nothing is calling for it, which usually points to a contactor welded shut. Code 74 is the reverse: the compressor should be starting but no voltage reaches it, so the contactor may be stuck open. A wiring error can cause either one.
Compatible models
Status light codes on Infinity two-stage outdoor units: the 24ANB7 air conditioner and 25HNB6/25HNB9 heat pumps.
Also shown as
With a stuck-closed contactor the outdoor unit may keep running after the thermostat is satisfied.
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 73 / 74
Shut off a unit that won't stop
If the outdoor unit runs with the thermostat off, switch off the disconnect next to it. Running nonstop can freeze the indoor coil in summer.
Book the repair
The contactor sits in the 230-volt control box, so there's nothing safe to check beyond the breaker and disconnect.
When to call a technician
Contactor replacement and wiring checks are technician jobs. Keep the outdoor power off until then if the unit won't stop on its own.
Parts linked to 73 / 74
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 73 / 74 code?
Status light codes on Infinity two-stage outdoor units: the 24ANB7 air conditioner and 25HNB6/25HNB9 heat pumps.
Can I fix Carrier 73 / 74 myself?
Only the basic checks. You can safely try the steps above, but 73 / 74 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
- 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.