2HUM18HC03/R2(DB)-SM  Wiring diagrams 
61
Domestic air conditioner
˄A˅
NO
YES 
Yes 
Check the indoor mainboard. 
No 
If the voltage is of a constant 
value of 0V DCto5V DC 
YES
measure the voltage between Jumpers 3 and 
4 of IC1 on the indoor mainboard with a 
multimeter. 
NO
The outdoor mainboard is damaged; 
Replace them with a new one. 
measure the AC voltage between positions 1 
and 3 on the terminal of outdoor unit with a 
multimeter. 
If 230VAC is available but 310DC not, 
the power module is damaged, replace i
with a new one. 
Test the outdoor power supply (230VAC 
and +310VDC) with a multimeter. 
The outdoor mainboard is damaged; replace 
it with a new one. 
The indoor mainboard is damaged; replace
it with a new one. 
If the value varies between 0 and 80 VAC, the
outdoor mainboard is damaged, replace it 
with a new one. 
If the value is constant at about 30V, the 
indoor mainboard is damaged, replace it with 
a new one. 
If both 230VAC and 310DC are 
available,measure +12V(from7805) 
is available.