Carrier / Comfort 22
Carrier PC03 error code
PC03 means the outdoor unit has detected low- or high-pressure protection. Pressure faults involve the refrigerant circuit and require professional diagnosis.
- Urgency
- stop use
- Verified
- Jul 31, 2026
- Fix path
- Technician
What it means
PC03 means the outdoor unit has detected low- or high-pressure protection. Pressure faults involve the refrigerant circuit and require professional diagnosis.
Urgency
Likely causes
- Carrier Table 4 identifies PC03 as pressure protection, low or high pressure.
- Carrier troubleshooting lists too much or too little refrigerant, blocked system circuit, dirty heat exchangers, and blocked airflow as possible causes.
Homeowner fix
Turn the system off. Clear only obvious outdoor obstructions and clean the indoor filter. Do not connect gauges or keep resetting; call a pro if PC03 returns.
When to call a pro
Call a licensed HVAC technician if PC03 returns. Tell them Carrier identifies PC03 as low- or high-pressure protection.
This code points to refrigerant or sealed-system and compressor work - get repair quotes from contractors in your area.
Get repair quotesRepair vs replace
This is normally a repair diagnosis, not an automatic replacement signal. If a technician confirms a major board, compressor, fan-motor, or sealed-system repair on older out-of-warranty equipment, compare the quote with replacement.
See Carrier mini-splitsYour Carrier model
Comfort 22 model pages in the Carrier catalog help compare this repair path with current replacement options.
- Carrier Comfort 22 9,000 BTU R-454B 115V (45MHHAQ09XC1 / 37MHRAQ09AA1)
Comfort 22
- Carrier Comfort 22 9,000 BTU R-454B 208/230V (45MHHAQ09XC3 / 37MHRAQ09AA3)
Comfort 22
- Carrier Comfort 22 12,000 BTU R-454B 115V (45MHHAQ12XC1 / 37MHRAQ12AA1)
Comfort 22
- Carrier Comfort 22 12,000 BTU R-454B 208/230V (45MHHAQ12XC3 / 37MHRAQ12AA3)
Comfort 22
For your technician
Technician note: follow R-454B/A2L practices; verify airflow, coils, metering/line restriction, pressure sensors/switches, leak/charge condition, and compressor operation. Page context: Carrier maps this display to the Comfort 22 line; source: Carrier 45MHHAQ High Wall Heat Pump Owner's Manual, Table 4 Error Codes; display convention: match the letter P, letter C, and three marker exactly before comparing neighboring codes.
Which systems show it
Comfort 22
Related troubleshooting
Use the symptom guide alongside the exact display code if the unit is flashing, cycling, or showing comfort symptoms.
Related codes
Source
- Document
- Carrier 45MHHAQ High Wall Heat Pump Owner's Manual, Table 4 Error Codes