Thermistor Check - Hoshizaki HUR40A(-D) Service Manual

C. Thermistor Check
A thermistor (semiconductor) is used for the cabinet control sensor and defrost termination
sensor. The resistance varies depending on temperature. No adjustment is required. If
necessary, check for resistance between thermistor leads and visually check the thermistor
mounting.
Temperature
°F
0 -17.8
10 -12.2
32
50
70
90 32.2
Cabinet & Defrost Thermistor T-R Curve
Temperature °F (°C)
To check a thermistor's resistance, follow the steps below.
1) Disconnect the connector for the thermistor in question under the control box and
behind the wire guard.
2) Remove the thermistor. See "IV.F. Removal and Replacement of Thermistors."
3) Immerse the thermistor sensor portion in a glass or cup containing ice and water for 2
or 3 minutes.
4) Check for a resistance between thermistor leads. Normal reading is from 5 to 6.5kΩ
for the cabinet and defrost thermistors and 145 to 175kΩ for the clogged filter sensor.
Replace the thermistor if it exceeds the normal reading.
°C Cabinet/Defrost Thermistors Clogged Filter Thermistor
14.2
10.7
0.0 6.0
10.0 3.9
21.1 2.5
1.6
Resistance (kΩ)
160
100
Clogged Filter Thermistor T-R Curve
Temperature °F (°C)
45
-
-
59
36