Maintenance Service and Trouble Shooting
avometer. If short circuit occurs or the resistance of a certain phase is low,
this means that short circuit does exist in the windings and/or between
turns, and insulation layers have been burned or deteriorated. A
megameter can be used in this inspection, too. I f the insulation resistance
is lower than 2 M
, this means that the insulation layer is already
breakdown. If the motor has been burned, repair it or replaced it with a new
one.
b) Fault of control relay
Analysis of Trouble
Overheat, burnout or wear of control relay contacts may occur generally.
All these will cause poor contact in electricity.
Remedy
Dismantle it to repair, or replace it with a new one.
c) Poor electric contactor in thermostat
Analysis of Trouble
Burnout of contactor and leakage of temperature sensing agent may
occur generally.
Remedy
Replace the old with a new one.
d) Check the terminals for loose connection and electric circuits for
other abnormal phenomena.
5) Mechanical faults of compressor
a) Seizing of shaft
This phenomenon is caused mostly by poor lubrication, such ad
insufficient quantity of lubricant, clogging in the lubricant oil line, or
intermittent lubricant oil supply. Dirt and other impurities in the lubricant oil
will increase its viscosity and cause the shaft to be seized. Copper plating
may also result in seizing of shaft.
b) Seizing of piston
This is caused by too small fit clearance between the piston and
cylinder or expansion due to heat.
Judgement of seizing shaft and piston: After the refrigerator has been
powered on, the compressor will not start and run, but a slight hum sound
can be heard, and several seconds later, thermal protective relay will
actuate and make the contacts open; this process will occur repeatedly, but
the compressor cannot be started.
E. Compressor won't stop
Sometimes, the compressor will run continuously(for several hours or
run without end), If the food placed in the refrigerator is not too much, there
may be the following two situations: i) the refrigerator very low, this means
that the control system is probably out of order; ii) the control system works
normally, and there are troubles in the refrigerating system or other parts.
1) Temperature is set improperly
a) The temperature control knob is set to the "coldest" position. This
23
