Thermistor
Common temperature-sensing fault part. Confirm resistance range and connector.
Hoshizaki E9 Error Code — What It Means
E9 on a Hoshizaki ice machine indicates a fault with the evaporator temperature sensor (also called the freezing plate thermistor or evaporator thermistor). The control board monitors this sensor to regulate the freeze cycle duration and determine when the ice sheet has reached proper thickness. When the control board detects that the sensor is reading out of range, open, or shorted, it displays E9 and halts ice production to prevent damage from an uncontrolled freeze cycle.
Common Causes
- Failed thermistor — The evaporator sensor has failed open or short. Thermistors on commercial ice machines degrade from thermal cycling and moisture exposure over years of operation.
- Loose sensor connector — The thermistor plug has vibrated loose from the control board connector or from the sensor clip on the evaporator.
- Damaged sensor wire — The wire between the evaporator thermistor and the control board has broken or developed a high-resistance connection, especially where it passes near the evaporator frost line.
- Faulty control board thermistor input — The input circuit on the Hoshizaki control board has failed, misreading a good sensor as faulty.
Step-by-Step Fix
- Locate the evaporator sensor — The E9 sensor is the thermistor clipped or attached to the evaporator (freezing grid or plate). On Hoshizaki crescent-cube machines, it is typically clipped to the evaporator manifold or inlet tube.
- Inspect the sensor and connector — Check that the thermistor is properly clipped in its correct location and has not fallen out of the mounting point. Check the connector at the board for loose pins.
- Measure sensor resistance — Disconnect the thermistor from the control board and measure resistance with a multimeter at the sensor leads. At 77°F (25°C), Hoshizaki evaporator thermistors typically read approximately 5–10 kΩ. An open (OL) or short (near 0Ω) confirms failure.
- Compare to a known good temperature — If you have a thermometer reading of the sensor environment, cross-reference the expected resistance from the Hoshizaki service manual thermistor chart to confirm the sensor is out of spec.
- Replace the evaporator thermistor — Order the Hoshizaki OEM evaporator sensor for your machine model. Clip it into the correct mounting location on the evaporator and reconnect the harness.
- Inspect the wiring harness — If the sensor resistance was normal but E9 persisted, check the full harness from sensor to board for broken conductors or corroded connections.
- Reset and test — Restore power and run a full ice production cycle. Confirm E9 is cleared and the machine harvests ice correctly.
Parts Often Needed
| Part | Notes |
|---|---|
| Evaporator thermistor (E9 sensor) | OEM Hoshizaki part; match to machine model number |
| Sensor wiring harness | Replace if conductors are broken or connector pins corroded |
| Control board | Replace only if all sensors and wiring test good |
Technician Tips
When diagnosing commercial refrigeration faults, start with the controller’s alarm history. Most digital controllers (Dixell, Carel, Eliwell) store the last 5-10 alarms with timestamps. An E1 alarm that appears consistently every few hours suggests a sensor going bad — the resistance value drifts until it’s out of range. An intermittent HI/LO alarm that appears only during hot afternoons suggests a condenser issue, not a sensor fault.
Prevention: Schedule quarterly condenser coil cleaning. Dirty coils are the #1 cause of high-head-pressure faults and compressor overheating in commercial refrigeration. Use a soft brush and compressed air — never a pressure washer on the coil fins.
Need Replacement Parts?
Before ordering, match the ice-machine part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If the replacement thermistor does not clear E9, the control board input circuit has likely failed. Contact a Hoshizaki-authorized service agent for control board diagnosis and replacement.