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Maintenance Service and Troubleshooting
b. Check the compressor accessories, including its thermal protector and
relay. If the thermal protector is damaged, the compressor cannot be
powered on. If the relay is out of order, the motor will not run and a
humming will sound when the compressor is turned on. If this happens,
shut it down immediately or the motor windings will burn out if this
condition persists.
c. Check the relay contacts and plugs to see if they are in perfect order and
working. Poor contact may cause the motor to stop running or to hum.
2. Check if circuit voltage is normal
Analysis of Problem
If the circuit voltage is lower than its rated value, it will be difficult to start the
motor, and a humming will be heard.
Solution
Measure the voltage with a voltmeter. If it is too low, instruct the owner to buy
a stabilizer to increase the voltage for normal operation.
3. Check if contacts of thermal relay are closed
Analysis of Problem
The contacts of the thermal relay are sometimes open due to a leakage of
temperature-sensing agent from the temperature sensor.
Solution
Remove the relay cover to check its contacts. If they are open, this means
the original setting was not properly positioned or the temperature-sensing agent
has leaked. Adjust the contacts of the temperature sensor towards the low
temperature direction. Once completed, check if contacts have been closed. If
they are still open, dismantle the temperature-sensing disc and immerse it into
warm water to see if the contacts activate. If they do not, the temperature-
sensing agent has leaked out, and the thermostat must be replaced.
4. Motor problems and other electrical failings
4a. Motor windings have been burned or short-circuited between cycles
Analysis of Problem
When motor windings have been burned or short-circuited, the fuse will blow
repeatedly, especially when the light switch is closed.
Solution
Check the terminals and outer casing to see if they are short-circuited, and
measure the resistance of each phase with a voltmeter. If short-circuited or the
resistance of a phase is low, this means the windings are short-circuited and/or
the insulation layers have deteriorated or been burned.
A multimeter can also be used. If the insulation resistance is lower than two mega
ohms (Ω), this means that the insulation layer is damaged. If the motor has been
burned, repair it or replace it with a new one.
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