AU-A18 (serv.man8). Troubleshooting - Sharp Air Conditioner Service Manual (repair manual). Page 3

18

The room is not cooled at all
or not cooled.
The compressor does not operate.

Measure resistances of TH1 and TH2.

Push the button "AUX." on 
the  indoor unit, for more than 5 sec.

Is the voltage

between terminal "N" and

"1" of the terminal board the

power supply voltage ?

Are the resistances

conformed Fig. 1 ?

Replace the thermistor ass'y 
with a new one.

NO

YES

YES

NO

Replace the PWB ass'y with a new one.

Using a tester, measure voltage at
the terminals on the terminal board.

100

80

60

40

20

0

-10

0

10

20

30

40

Resistance

Thermistor

Room temperature

Heat exchange

Color

Yellow

Orange

To measure the resistance, first remove 
the connector as shown at right.

Room temperature 

thermistor TH1

Tester

Connector

No. 3 to 4

No. 1 to 2

K

Heat exchange thermistor 
TH2 (orange)
25

°C resistance 15 K 

Room temperature 
thermistor TH1 (yellow)
25

°C resistance 10 K

Heat exchange 

thermistor TH2

Tester

4

1

CN4

The control circuit is normal.
   The compressor may be defective.
   The running capacitor may be 
   defective.
   Refrigerant may be leaked.
   The outdoor fan motor may be 
   defective.
   The outdoor fan motor capacitor 
   may be defective.