Hoshizaki 73168 service manual Defrost Thermistor cabinet Malfunction Alarm E8, Possible Causes

5. Defrost Thermistor (cabinet) Malfunction Alarm (E8)

If the control board detects an open defrost thermistor, "E8" is displayed. When the control board detects a shorted defrost thermistor, a 10-minute delay timer begins. After the 10‑minute delay timer expires, "E8" is displayed. To bypass the 10-minute delay timer, move the power switch to the "OFF" position. Then, while pressing the rail "SET" button, move the power switch to the "ON" position.

•If this alarm appears, first make sure that the thermistor is properly connected to the control board.

•A shorted defrost thermistor is not detected by the control board during the 1st hour after power is turned on. To bypass the 1-hour delay timer, move the power switch to the "OFF" position. Then, while pressing the rail "SET" button, move the power switch to the "ON" position.

Reset Options

The alarm automatically resets when one of the following conditions is met:

•The defrost thermistor is secured to the control board.

•The defrost thermistor is within normal operating range. For details, see "II.E. Thermistor Check."

•A functioning defrost thermistor is installed.

Possible Causes

•Trouble with the defrost thermistor. For checkout procedure, see "II.E. Thermistor Check."

•Trouble with the control board reading the defrost thermistor.

E8 Alarm
Timer Start	E8 Alarm Timer Start
Under 10 min.	10 min.

E8 (short circuit )
Detection Point	E8
122°F (50°C)
	Alarm
E8 Alarm (open circuit)
Detection Point
-67°F (-55°C)

Temperature Display

E8 Alarm (short circuit) Reset

E8 Alarm (open circuit) Reset

E8

Alarm

Temperature

Display

E8	E8
Blinking	Blinking

5a. Secondary Defrost Thermistor (Rail, not used)

The secondary defrost thermistor (located behind the wire cover) is not used for operation of the unit. It is used for control board programming and should not be removed. An "E8" alarm occurs when the secondary defrost thermistor is removed or fails. For details, see "III.A.6. Defrost Thermistor (cabinet) Malfunction Alarm (E8)."

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