Thermistor Failure - U-Line 1224RF 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 -40
-31 -35
-22 -30
-13 -25
-4 -20
5 -15
14 -10
23 -5
32 0
41 5
50 10
59 15
68 20
77 25
86 30
95 35
104 40
113 45
122 50
131 55
140 60
u-line.com
Nominal Resistance
(OHMS)*
169157
121795
88766
65333
48614
36503
27681
21166
16330
12696
9951
7855
6246
5000
4029
3266
2665
2186
1803
1495
1247