Service diagnosis
29 Domestic air conditioner 
10.Service Diagnosis
10.1 Caution for Diagnosis
The operation lamp flashes when any of the following errors is detected.
●
 
1. When 
a protection device of the indoor or outdoor unit is activated or when the thermistor malfunctions,
disabling equipment operation. 
2. When 
a signal transmission error occurs between the indoor and outdoor units. In either case, conduct
the diagnostic procedure described in the following pages. 
10.2 Problem Symptoms and Measures 
Symptom  Check Item  Details of Measure 
None of the units 
operates 
Check the power supply. Check to make sure that the rated voltage is supplied. 
Check the indoor PCB  Check to make sure that the indoor PCB is broken 
Operation 
sometimes stops. 
Check the power supply.
A power failure of 2 to 10 cycles can stop air conditioner 
operation.
●
 
Equipme
nt 
operates but does 
not cool, or does 
not heat (only for 
heat pump) 
Check for faulty operation 
of the electronic 
expansion valve. 
Set the units to cooling operation, and compare the 
temperatures of the liquid side connection pipes of the 
connection section among rooms to check the opening and 
closing operation of the electronic expansion valves of the 
individual units. 
Diagnosis by service port 
●
pressure and operating 
current. 
Check for insufficient gas. 
Large operating 
noise and 
vibrations 
Check the installation 
condition. 
Check to make sure that the required spaces for 
installation (specified in the Technical Guide, etc.) are 
provided.