Unit shuts down during or after harvest; control board beeps four times repeatedly

Safety First: Disconnect power before accessing internal components. Avoid bending refrigerant lines.

• Locate thermistors: On most Hoshizaki models, there is an evaporator thermistor clipped to the evaporator plate and sometimes a discharge line thermistor on the compressor discharge line.
• Inspect mounting: Ensure each thermistor is firmly clipped to clean metal surface. If loose or hanging, reattach with the proper clip or thermal compound as specified by Hoshizaki.
• Check for damage: Look for cracked sensor heads, cut wires, or corroded connectors. Repair or replace damaged wiring.
• Test resistance: With power off, disconnect the thermistor from the board and measure resistance with a multimeter. Compare to Hoshizaki service manual temperature/resistance chart (e.g., around 5–10 kΩ at room temperature depending on model). Replace if readings are far out of spec or open/shorted.
• Reset and monitor: After replacing or reseating thermistors, restore power and reset the unit. Monitor operation through at least one full freeze and harvest cycle.

When to call a technician: If thermistors test good but the 4-beep code persists, the control board’s temperature sensing circuit may be defective or there may be a true high-temperature condition due to sealed system issues.