13
Models 358 & 359
Controls & Systems
Service Tips
If a problem arises with the thermistor control
assembly, identify and replace only the faulty
component. For example, if the probe is defective,
replace only the probe.
S
A varistor must be connected to the
thermistor control 24 VAC terminals in order
to protect the control from voltage spikes
(varistor part number X31547).
S
Fill the bulb-well with antifreeze before
installing the thermistor probe.
S
Be sure the probe is installed completely
into the bottom of the bulb-well.
Note:
Lower the probe to the point where the wires
extend from the probe and a resistance is felt. This
indicates the probe is installed completely in the
bottom of the bulb-well.
If the thermistor relay which
starts
the compressor
will not close, check the following items:
ELECTRICAL SHOCK AREA! USE CAUTION!
1.
Make sure power is being supplied to the
freezer and that all operating switches are in
the correct position.
2.
Using a voltmeter, check the voltage supply to
the thermistor control. The control requires 24
volts to operate.
3.
Using an ohmmeter, check probe resistance.
(Refer to the thermistor curve chart on page 14
for proper readings.)
If the thermistor relay which
deactivates
the
compressor will not open, check the following items:
ELECTRICAL SHOCK AREA! USE CAUTION!
1.
Make sure the thermistor relay opens when the
freezer control switch is in the “OFF” position.
2.
Make sure the thermistor probe is connected to
the correct probe terminals.
3.
Using an ohmmeter, check the thermistor probe
for proper resistance. (Refer to the thermistor
curve chart on page 14 for proper readings.)
4.
Disconnect one wire to an anticipator terminal.
If the thermistor relay opens after
approximately 25 seconds, the problem is in the
anticipator wiring circuit.
When problems such as erratic product quality
occur, it is of utmost importance to determine if the
thermistor components are defective before
replacing them.
For a diagram of the thermistor control, see
page 18 (Troubleshooting Thermistor
Components).
