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5.2 THERMISTORS
The refrigerated drawers utilize two thermistors: one is known as the evaporator thermistor and the other as the display thermis-
tor. Each thermistor has a dierent function for input to the electronic control.
Evaporator thermistor:
The evaporator thermistor turns the unit on and o. It is secured to the evaporator or cabinet liner.
Display thermistor:
The display thermistor is connected to the LED display and displays the temperature inside the unit on the display panel.
The following will happen in the event of one or both thermistors fail:
If the evaporator thermistor fails, all loads will be shut o and the unit will not run.1.
If the evaporator thermistor senses temperature outside of 0-140 degrees F, all loads will be shut o and the unit will not run.2.
The display panel will ash E3 for an evaporator thermistor failure and E4 for a display thermistor failure. If both thermistors 3.
fail, the error codes will be displayed sequentially. An audible alarm will also sound six times every minute if either one or
both thermistors fails.
The thermistor can be checked by use of a multimeter with the ability to read resistance. To check the thermistor:
Disconnect and remove thermistor from unit.1.
Use a reference temperature point that is know (such as an ice bath) and measure the resistance across the wire leads.2.
Compare the recorded resistance with Table C.3.
If measured resistance falls outside the resistance given in Table C within 4% of the value, the thermistor is bad and will need to be
replaced.
Table C: Resistance versus Temperature Chart
Temperature (C) Temperature (F) Resistance (K-OHMS)
-15 5 11.350
-10 14 8.918
-5 23 6.700
0 32 5.630
5 41 4.520
10 50 3.652
15 59 2.970
20 68 2.430
25 77 2.000
If the thermistor has been tested and is found to be good, check the temperature of the evaporator plate and the resistance of the
thermistor. If the temperature of the evaporator plate does not correspond to a proper resistance from the thermistor, check for a
proper and secure connection of the thermistor to the evaporator plate bracket.
SYSTEM COMPONENTS
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