Carrier 38QUS014DS2-2 Service Manual page 85

18.3.3.6 Low pressure protection (ODU P2)(For38QUS036DS4*, 38QUS042DS5*)
Low pressure protection
Low pressure protection
Whether the wiring
Whether the wiring
between the low pressure
between the low pressure
protector and main control
protector and main control
board is connected well or
board is connected well or
correctly
correctly
Yes
Whether the low
Whether the low
pressure protector
pressure protector
is broken
is broken
Method: Disconnect the plug.
Method: Disconnect the plug.
Measure the resistance of the
Measure the resistance of the
low pressure protector. If the
low pressure protector. If the
protector is normal the value is
protector is normal the value is
o
o
Yes
Check whether the outdoor
Check whether the outdoor
ambient temperature is too
ambient temperature is too
low
low
No
Check whether valve core
Check whether valve core
of high pressure valve is
of high pressure valve is
opened
opened
Yes
Check if the indoor fan runs
Check if the indoor fan runs
properly in cooling mode
properly in cooling mode
Yes
Replace outdoor main board
Replace outdoor main board
No
Refrigerant is not enough add the
Refrigerant is not enough add the
refrigerant
refrigerant
No
Check whether the refrigerant
Check whether the refrigerant
system is ok
system is ok
No Connect it well
Connect it well
Replace low pressure protector
No
Replace low pressure protector
Yes Stop the unit
Stop the unit
Open fully valve core of
Open fully valve core of
No
high pressure valve
high pressure valve
please refer to the solution of fan
please refer to the solution of fan
speed has been out of control
speed has been out of control
No
malfunction. Find out the cause and
malfunction. Find out the cause and
have it solved.
have it solved.
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