The Q111 and Q911 is a MOS-FET and its gate terminal is a high impedance. When a probe such as a multimeter is
contacted with the gate G , the Q111 and Q911 may have the continuous ON state to supply overcurrent in the circuit,
causing the ICP1 and ICP3 blowout and Q111 and Q911 failure.
When checking the switching waveform of the Q111 and Q911, set the source S to the base and measure the gate G and
drain D .
(4) During power feeding to the P.W.B., do not remove and insert the CN10 (fan motor connector) and CN11 (Vertilation fan
motor connector). Failure to do so may cause overcurrent to the fan motor and P.W.B.s (microcomputer, IC and the like)
and a failure may occur. To remove or insert the CN10 and CN11, be sure to shut off the power.
(3) When checking the voltage and waveform, do not connect the probes to the forbidden areas show below. Touching them
may cause the ICP1 and ICP3 blowout and Q111 and Q911 failure.
(2) The CN3 (power suppy) and CN7 (temperature fuse) and CN10 (fan motor) and CN11 (ventilation fan motor) are the
connectors with lock mechanism.
Press the lock with your fingers to unlock and remove the connector.
1. Use due caution for short circuit in servicing.
Short circuit will open the ICP immediately.
2. When the ICP opens, remove the cause of this phenomenon and replace the ICP.
If the remedy is improper, the ICP may open again.
Other Cautions
(1) Cautions concerning ICP (IC Protector)
35V line
12V Power circuit
ICP2
ICP1
ZD121
5V
Power circuit
Ventilation fan motor
12V Power circuit
Press here
Unlock
Lock
Ventilation fan motor
Indoor unit fan motor
12V line
5V line
20V
Zener Diode
0V
ICP3
M
M
R121
R920
R921
ICP3
ICP1
R111
ZD111
ZD911
R911
C911
C111
C102
Q113
0V
35V line
+
_
Q913
R914
Q912
R915
OK
OK
OK
OK
Q111
Q911
R114
S
D
G
S
D
G
Q112
R115
Forbidden
Forbidden
area
area
Forbidden
area
Forbidden area (Gate(G)-0V)
Forbidden
Forbidden
area
area
Forbidden
area
Forbidden area (Gate(G)-0V)
8
7
6
1
4
3
2
5
8
7
6
1
4
3
2
5
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