Low Pressure Check; Low - Daikin RXQ12AHR Service Manual

Check
6.2

Low Pressure Check

CHECK 2 Referring to the Fault Tree Analysis (FTA) shown below, probe the defective points.
Defective
low pressure
control
Abnormally low
In cooling
pressure
If the indoor unit
(Low evaporating
electronic
temperature)
expansion valve is
throttled too much:
Defective electronic
expansion valve
control
Low suction
air temperature
of the
evaporator
Less
circulation
quantity of
refrigerant
Degradation
in condensing
capacity
Reference
CHECK 7 Refer to page 293.
288
Defective low pressure sensor
Defective
compressor
Defective outdoor unit main PCB
capacity
control
Defective low pressure sensor
Defective
low pressure
Defective hot gas solenoid valve
protection
control
Defective outdoor unit main PCB
Defective indoor
Defective valve coil
unit electronic
expansion valve
Defective valve body
Defective gas pipe
thermistor of indoor unit
Defective
control
Defective liquid pipe
thermistor of indoor unit
Defective outdoor unit main PCB
Low suction air
Short circuit
temperature of
Low room temperature
indoor unit
Defective suction air thermistor of indoor unit
Abnormal piping length
High pipe
Bent or crushed pipe
resistance
Clogging of foreign particles
Stop valve closed
Refrigerant shortage
←
Refer to CHECK 7 .
←Eliminate moisture by vacuum operation.
Moisture choke
Dirty
←Is the heat exchanger clogged?
evaporator
Decreased
fan output
Decreased
fan airflow
High airflow
rate
passage
resistance
←Is the pressure value checked with the Service Checker
corresponding to the measurement of the pressure sensor?
←Are the voltage characteristics normal?
←Is the pressure value checked with the Service Checker
corresponding to the measurement of the pressure sensor?
←Are the coil resistance and insulation normal?
←Are the voltage characteristics normal?
←Are the coil resistance and insulation normal?
←Check for the thermistor resistance and connection.
←Check for the thermistor resistance and connection.
←Are the voltage characteristics normal?
←Is the suction air temperature not less than 14°C
←Is the indoor temperature not more than 14°C
←Is the connector properly connected?
Are the thermistor resistance characteristics normal?
←Does the piping length fall in the permissible range?
←Conduct visual checks for pipe conditions.
←Is there any temperature difference caused before
and after the filter or branch pipe?
←Check to be sure the stop valve is open.
←Can the fan motor be rotated with hands?
Defective fan motor
Are the motor coil resistance and insulation normal?
Defective outdoor unit
←If a spare PCB is mounted, is the capacity
main PCB (Including
setting properly made?
capacity setting)
←Is the air filter clogged?
Dirty filter
←Is there any obstacle in the air passage?
Obstacle
SiAF341904E
Part 6 Service Diagnosis