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 indo
●
or 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  Che
●
ck 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. 
Equipment 
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.