Thermistor Failure - U-Line U-1224WCS-13B User Manual & Service Manual

USER GUIDE
SAFETY • INSTALLATION & INTEGRATION • OPERATING INSTRUCTIONS • MAINTENANCE • SERVICE
Thermistors
Thermistors are used for various temperature readings.
Thermistors provide reliable temperature readings using a
resistance which varies based on surrounding
temperatures. If a faulty thermistor is suspected it may
be tested using an accurate ohmmeter.
Both thermistors in the unit are identical. If a thermistor is
suspected of being defective, the resistance can be
verified. Place the thermistor in an ice water bath, the
resistance should read 16.1k OHMs +/-5% on your meter.
Thermistor connections must be kept clean. A thermistor
connection that has become corroded can cause
resistance values from the thermistor to change as they
pass through a dirty connection to the board.
It is for that reason that we apply dielectric grease to all of
our thermistor connections. Dielectric grease will help to
keep thermistor connections clean and dry.
If you change a thermistor in the unit please re-apply
dielectric grease to the connection. If you encounter a
dirty thermistor connection, you should replace the
thermistor and the thermistor harness.
Thermistor error information can be found in the Control
Operations - Service section.
This unit has two thermistors.
Thermistor one (Zone):
Located along the right hand side wall. It is used to
maintain the operating temperature within that zone.
Thermistor two (Evaporator):
Located on the evaporator. It is used for defrost.

THERMISTOR FAILURE

Zone Thermistor
If the zone thermistor in the unit fails, the unit will
continue to cool in a backup mode (Self Preservation
Mode) to preserve the integrity of the contents. The unit
will otherwise operate normally.
1000 Series Self Preservation Mode:
The unit will cycle on for 10 minutes then off for 40
minutes.
Evaporator Thermistor
If the evaporator thermistor fails, the unit will rely on a
preset defrost timer during defrost cycles. The unit will
otherwise operate normally. Refer to defrost section.
Thermistor Resistance Data
Temp (F) Temp (C)
-40
-31
-22
-13
-4
5
14
23
32
41
50
59
68
77
86
95
104
113
122
131
140
149
158
167
176
* (+/-5%)
56
Nominal Resistance
(OHMS)*
-40 169157
-35 121795
-30 88766
-25 65333
-20 48614
-15 36503
-10 27681
-5 21166
0 16330
5 12696
10 9951
15 7855
20 6246
25 5000
30 4029
35 3266
40 2665
45 2186
50 1803
55 1495
60 1247
65 1044
70 879
75 743
80 631
Thermistor 1