York DHP30NWB21SDCP30NWB21SDHP36NWB21SDCP36NWB21S Service Manual page 57

(2) IPM Protection, Out-of-step Fault, Compressor Phase Overcurrent (AP1 below refers to the outdoor control panel)
Main check points:
If the connection between control panel AP1 and compressor COMP is secure? If loose? If the connection is in correct order?
If the voltage input of the machine is within normal range? (Use AC voltmeter to measure the voltage between terminal L and
N on the wiring board XT)
If the compressor coil resistance is normal? If the insulation of compressor coil against the copper tube is in good condition?
If the working load of the machine are too high? If the radiation is good?
If the charge volume of refrigerant is correct?
Fault diagnosis process:
Energize and
switch on
IPM protection
occurs after the
machine has run for
a period of time?
Refer to the
Electrical Wiring
Diagram and check
if the connection
between AP1 and
COMP is loose and if
the connection order
is correct.
If the connection
between AP1 and
COMP is unsecure
or the connection
order is wrong?
Use ohmmeter to
measure the resistance
between the three
terminals on compressor
COMP, and compare the
measurements with the
compressor resistance on
Service Manual.
Use ohmmeter to
measure the resistance
between the two
terminals of compressor
COMP and copper tube.
Please confirm:
1. If the indoor and outdoor heat exchangers are dirty? If they are obstructed by other objects which affect the
heat exchange of indoor and outdoor unit.
2. If the indoor and outdoor fans are working normally?
3. If the environment temperature is too high, resulting in that the system pressure is too high and exceeds the
Y
permissible range?
4. If the charge volume of refrigerant is too much, resulting in that the system pressure is too high?
5. Other conditions resulting in that the system pressure becomes too high.
If there is any
abnormality
described above?
N
Connect the control panel
AP1 and compressor
COMP correctly according
Y
to the Electrical Wiring
Diagram. Then, energize
and start the unit.
If the
resistance is
N
normal?
Resistance higher
than 500MΩ?
Y
Replace the
control panel
AP1
END
Take corrective actions
according to Technical
Y
Service Manual, and
then energize and start
the unit.
Replace the
control panel AP1
If the unit can
work
normally?
Replace the
compressor
COMP
N
If the unit can
Y
work normally?
N
Y
50