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Temperature Monitoring
There are a total of six thermistors involved in making
decisions that affect the running speed
of the compressor. They are:
Ambient Temperature Thermistor
Fresh Food Section Thermistor
Evaporator Thermistor
Freezer Section Thermistor
Upper FoodSaver™ Thermistor
Lower FoodSaver™ Thermistor
Information from these six locations is provided to
the Main Board and the correct run speed for the
compressor is determined. Failure of a thermistor will
result in incorrect system operation.
If either the fresh food or freezer thermistor opens
the system will assume that the temperature is well
below the desired temperature and no cooling will
be provided. If the thermistor shorts, the system will
assume the temperature in the cabinet is much too
warm and the compressor will run constantly in an
effort to satisfy the Main Control Board.
The ambient temperature sensor is used to monitor
room temperature. The air heading into the condenser
is sampled. Since ambient conditions affect the
system’s ability to transfer heat to the environment,
this measurement is used to help set the speed of
the compressor. If this thermistor were to fail, the
compressor may not run at the most efficient speed
to keep the interior cool but the proper cabinet
temperatures should be maintained.
Page 2-4
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FREEZER
DOOR
ON
ALARM
REFRIGERATOR
WATER FILTER
WORKING
RESET
POWER
INTERRUPT
ORDER
REPLACE
UNIT
ON
POWER
SERVICE
3
4
2
1
6
5
NOTE (CONTINUED)
If you can adjust temperature on one FoodSaver™ assembly but not the other, check the
connections to the non-functioning unit. If data is present at the connector, the fault is likely to
be in the FoodSaver itself. If data is not present at the connector suspect a fault between the
Main Board and the FoodSaver. A similar process can be used with any of the components on
the data communication system.
Verification of the data will be different for almost every model of multimeter. The data signal
is a five volt Peak to Peak square wave. The frequency and duty cycle of this wave form will be
constantly changing. Many voltmeters will detect this signal as approximately 2.5VAC. Similarly,
the DC range on many meters will detect 2.5VDC. If using a frequency counter you will see the
frequency vary as the data itself changes. Readings of a constant 0VAC or 0VDC would in most
cases indicate an absence of information on the data lines.
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