21L
Low Refrigerant Pressure Lockout
This code typically points to
- Low refrigerant charge
- Failed indoor blower motor
- Dirty return filter
- Failed EXV
- Refrigerant-circuit restriction
- Inadequate indoor airflow
Next checks to confirm
- Evaluate low-pressure condition
- Inspect airflow, charge, EXV, and refrigerant restrictions
Escalation
3 low-pressure faults in same cooling call OR during 120 minutes of continuous heating locks compressor out; Control Center displays low-pressure lockout
Reset behavior
If heating-mode lockout occurs below -10°F outdoor ambient, auto-reset when ambient rises to -10°F; otherwise manual reset by removing power to both indoor and outdoor units for 1 minute.
Urgent
Fix now