Johnson Controls DHW18CMB21S Service Manual page 25

● If the resistance of compressor coil is normal? If the isolation of compressor coil with copper pipe is good?
● If the unit is overloaded? If the heat radiation of the unit is good?
● If the refrigerant charge is suitable?
Flow chart:
yes
17
Energize the unit
Please check:
1. if the indoor and outdoor heat exchanges are
dirty, if there is obstacle to affect the radiation;
2. if the indoor and outdoor fans are running
normally;
3. if the pressure of the system is too high;
4. if the refrigerant is too much which causes
the high level of pressure;
If the wire of compressor is connected
well and correctly?
yes
Test the resistance between
the three phases
If the resistance is normal?
yes
Test the isolation impedance
between the three phases of the
compressor and thecopper pipe
If the resistance is above 500M
no
Replace the
compressor
Malfunction is eliminated
no
Replace the outdoor
mainboard
End
If the above cases are existed?
no
Reconnect the wire of the
compressor according to the
correct wiring method
no
?
yes
yes
no
Correct according to the service
manual and then energize the
unit to operate