Mitsubishi SUZ-KA35VA Service Manual page 73

The thermistors in the outdoor unit are abnormal.
Check of outdoor thermistors
G
Defrost thermistor RT61
Measure the
resistance
between CN641
and .
Discharge
temperature
thermistor RT62
Measure the
resistance
between CN641
and .
Fin temperature
thermistor RT64
Measure the
resistance
between CN642
and .
Ambient
temperature
thermistor RT65
Measure the
resistance
between CN643
and .
Check of R.V. coil
H
First of all, measure the resistance of R.V. coil to check if the coil is defective. Refer to 12-4..
In case CN721 is not connected or R.V. coil is open, voltage is generated between the terminal pins of the connector although no
signal is being transmitted to R.V. coil. Check if CN721 is connected.
Unit operates COOL mode even if it is set to HEAT mode.
Disconnect connector (CN61) between
compressor and intelligent power module.
[For wireless remote controller use model]
Turn ON the power supply and press the
EMERGENCY OPERATION switch
(HEAT switch).
[For wired remote controller use model]
Turn ON the power supply and press the
TEST button twice (HEAT mode).
Unit operates HEAT mode even if it is set to COOL mode.
Disconnect connector (CN61) between
compressor and intelligent power module.
[For wireless remote controller use model]
Turn ON the power supply and press the
EMERGENCY OPERATION switch
(COOL switch).
[For wired remote controller use model]
Turn ON the power supply and press the
TEST button twice (COOL mode).
OC322G
Disconnect the connectors CN641, CN642 and CN643 from the inverter P.C. board.
(Check the characteristics of each thermistor.)
Is the resistance of
Yes
thermistor normal?
(Refer to 12-6.1.)
No
Replace the
thermistor
except RT64.
In case that
RT64 is
abnormal,
replace the
inverter P.C.
board, since
RT64 is
combined with
the inverter P.C.
board.
Is there 230V AC between CN721
on the power P.C. board 3 minutes after
the power supply is turned ON?
Replace the 4-way valve.
Is there 230V AC between CN721
on the power P.C.board 3 minutes after
the power supply is turned ON?
• Defective R.V. coil
• Defective 4-way valve
73
Reconnect the
connectors
CN641, CN642
Replace the inverter
and CN643.
P.C. board.
Turn ON the
power supply and
press
EMERGENCY
Does the unit operate
OPERATION
10 minutes or more?
switch (For
wireless remote
controller use
model)./TEST
OK.
button twice (For
(Cause is poor
wired remote
contact.)
controller use
model).
and
Yes
and
No
[SUZ-KA25/35VA(H).TH]
No
Yes
No
Replace the
power P.C. board.
CN721
Power P.C. board
(soldered side)
Yes
Replace the
power P.C. board.