Daitsu DS-9KIDR - Cooling System Gas Flow Abnormal Protection

Air Conditioner Service Manual
55
3.2.16 F4---Cooling system Gas flow abnormal protection
When compressor startup, unit will check the variation of IDU coil temperature. If there is mistake installer forgetting
to open the 2-way or 3-way valve on ODU, the gas can’t flow in the cooling system, it will show F4 protection.
Start
Display F4
Open the valve
No
End
Check the 2-way
valve and 3-way
valve opened？
No
Yes
No
F4 disappear?
The IPT sensor
open or short?
Replace the sensor
Yes
Yes
No