E-06001 (1/1)
<<All Products>>
Replacement of Magnetic Switch or Magnetic Contactor in Case of
Compressor Failure
Applicable models:
All models
A case was reported where a new compressor, which replaced the defective compressor, failed to operate
soon because the magnetic switch had been broken. A method of magnetic switch troubleshooting in case
of compressor failures is shown below.
[Thorough request]
If the compressor of an air conditioner fails to operate, inspect the magnetic switch or magnetic contactor.
If the magnetic switch or magnetic contactor is judged to have a defect, make proper parts replacement.
[Inspection points]
1) Weld inspection of magnetic switch
After turning the power OFF, use a circuit tester and make a resistance check between the R and U
terminals, the S and V terminals, and the T and W terminals in pairs, respectively. Unless the
resistance between each pair of these terminals is infinite, it is likely that the contacts of the magnetic
switch are welded.
2) Contact bounce inspection
After turning the power ON (with an operation reference provided), make a voltage check between the
U and V phases, the V and W phases, and W and U phases in pairs, respectively. Unless the voltage
between each pair of these phases is the same as the power supply voltage, it is likely that contact
loss has been resulted.
3) Operating sound check
• If the operating sound is dull when the contacts are turned ON, it is likely that the contacts are
affected by foreign matter. The contacts must not rattle. They must snap sharply.
• The coil may have been burned off if no operating sound is heard.
4) Cases requiring replacement of both magnetic switch and magnetic contactor.
Refer to the following table to make an inspection and remedy the problem according to the
compressor failure mode.
Compressor failure mode
Compressor
Breaker
Constant
speed
With electric leakage detector
U
Phase
short-circuiting
¯
With no electric leakage detector
U
¯
Inverter
Mechanical lock
Ground fault
(insulation failure)
U
¯
With electric leakage detector
−
−
U
With no electric leakage detector
−
−
U
U: It is likely that there is a component failure. (Check the above inspection points)
¯: It is highly likely that there is a component failure.
5) If the compressor overheats and malfunctions without any refrigerant circuit problems (i.e., the
quantity of refrigerant is normal without defective factors, e.g., the closure of the stop valve or
refrigerant circuit clogging), it is likely that the compressor failure is transient or the compressor failure
occurred because the compressor in operation was overheated due to a contact weld.