R-Pro › Field cases › Heat pumps
EEV Hunting — Unstable Superheat Control
Likely causes
Inappropriate EEV PID parameters
Check: response cycle too fast
What to do: Check EEV controller parameters — set superheat target (normally 5~8K), dead-band 1~2K
Evaporator outlet temperature sensor fault or poor contact
Check: Inspect with instruments or visually
What to do: Measure evaporator outlet sensor resistance and verify tight mounting
Unstable evaporation pressure due to refrigerant overcharge or undercharge
Check: Inspect with instruments or visually
What to do: Check refrigerant charge — adjust to maintain suction superheat 5~8K
EEV stepper motor mechanical fault
Check: step loss
What to do: Power off EEV, issue manual full-open command to reset step count
PID not tuned for high load-variation environment
Check: Inspect with instruments or visually
What to do: Reroute inverter and EEV wiring separately; replace with shielded cable
On hunting, first reset EEV with full-open command and restart — immediately resolves step-loss cases.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
Open R-Pro →Related cases
- Ground Loop Antifreeze Concentration Insufficient — Freezing / Poor Heat Transfer
- Heating COP Drop at Low Outdoor Temp (Below -10°C)
- Discharge Air Temperature Below 40°C During Heating
- Excessive Frosting on Air-Source Outdoor Unit (Defrost Failure)
- Auxiliary Electric Heater (Backup Heater) Malfunction
- Refrigerant Undercharge/Overcharge — Winter-Specific Symptoms