Fault codes covered
33-15, 33-55
Code 33-15 will become active if compressor is running and discharge pressure is below the lower safe operating boundary for a period of time. Active envelope management will attempt to modify system operation to correct this condition before fault is set, but once time limit beyond the limit is exceeded the system will shutdown. 6 occurrences of code 33-15 within 2 hours will result in code 33-55 and 2 hour lockout.
Low discharge pressure can be caused by malfunctioning reversing valve, low charge, missing or stuck TXV/EXV, or compressor not operating properly.
Source: ACHPVSR454-02SM troubleshooting pages.