Friedrich MM18YJ, Service Manual

Page: 45 / 83

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Start
Is the supply voltage unstable with big fluctuation?
Is the supply voltage too low with overload?
Is the indoor / outdoor heat exchanger too dirty,
or are the air inlet and outlet blocked?
Measure the current of live wire
on the main board with a clamp ampere meter. Is the
current higher than the value of the overcurrent
protection?
Is the fan motor running abnormally; is the fan speed too
low or does it fail to run?
Is there blockage inside the system?
(Filth blockage, ice plug, greasy blockage, the Y-valve hasn’ t
been opened completely)
Is the compressor running
abnormally? Is there abnormal sound or oil leakage; is
the temperature of the shell too high, etc.?
no
no
no
no
yes
no
no
Replace the control
panel
End
Normal fluctuation is within 10% of the rated voltage on the
nameplate
yes
Malfunction is eliminated.
no
Adjust the supply voltage to maintain it within normal range
yes
Malfunction is eliminated.
no
Clean the indoor and outdoor heat exchangers and remove
the blockage of air inlet and outlet
yes
Malfunction is eliminated.
no
Check the motor and reinstall the motor to have the fan run
normally
yes
Malfunction is eliminated.
no
Replace the controller
no
Malfunction is eliminated.
no
Flush the heat exchangers with high pressure nitrogen
yes
Malfunction is eliminated.
no
Replace the compressor
yes
Malfunction is eliminated.
no
yes
yes
yes
yes
yes
yes
yes