Using performance data to troubleshoot a system. Listed below are potential causes that may directly result in poor performance issues. 

Potential causes for high head pressure:

• refrigerant overcharge
• non condensable in system
•  dirty/blocked condenser
• malfunctioned condenser fan motor
• restricted water flow
• higher than normal ambient temperature
• restriction in discharge line
• recirculating condenser air

Potential causes for low head pressure:

• low refrigerant charge
• lower than normal ambient temperature
• mechanical failure inside compressor
• major restriction

Potential causes for high suction pressure

• high evaporator load
• oversized metering device
• mechanical failure inside compressor
• flash gas entering the evaporator

Potential causes for low suction pressure

• low refrigerant charge
• restriction
• undersized, misadjusted, or faulty metering device
• low evaporator load (filters, ice, airflow)