Daikin REYQ-AATJA, Service Manual, Page: 396 / 495

Troubleshooting by Error Code SiUS372201EA
389 Part 6 Service Diagnosis
Note(s)
Reference
Reference
3.63 Refrigerant Shortage
Applicable
Models
All outdoor unit models
Error Code
U0
Method of Error
Detection
Detect refrigerant shortage according to a low pressure level or a difference in heat exchanging
temperature from the suction pipe.
Error Decision
Conditions
Low pressure becomes 0.1 MPa (14.5 psi) or less.

Error is not determined. The unit continues the operation.
Supposed
Causes
 Refrigerant shortage or refrigerant clogging (wrong piping)

Defective thermistor
 Defective low pressure sensor
 Defective outdoor unit main PCB
Troubleshooting
CHECK 2 Refer to page 425.
CHECK 12 Refer to page 437.
Is the low
pressure 0.1 MPa
(14.5 psi) or less?
(
∗
1)
Is the
characteristics of
low pressure sensor
normal? (
∗
2)
Replace the low pressure
sensor (S1NPL).
Replace the outdoor unit
main PCB (A1P).
NO NO
YES YES
Eliminate factors that cause
decreasing low pressure.
CHECK 2
Caution
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
(1) Mount a pressure gauge at the service port on the low
pressure side.
(2) Reset the operation using the remote controller then
restart.

1. Check the low pressure value by using pressure gauge in operation.

2. Compare the actual measurement value by pressure sensor with the value by the
pressure gauge.
(To gain actual measurement value by pressure sensor, measure the voltage at the
connector [between (2)-(3)] and then convert the value into pressure.
CHECK 12 )