Seivice diagnosis
Domestic air conditioner
11 Service Diagnosis
 
11.1 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. 
11.2 Parameter of primary electronic appliance 
11.3 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. 
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. 
 
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