14
Specifications are subject to change without notice.
© 2013 Mitsubishi Electric US, Inc.
Room temparature
thermistor
(TH21)
Liquid pipe thermistor
(TH22)
Gas pipe thermistor
(TH23)
Transformer 24V
Disconnect the connector, then measure the resistance using a tester.
(Sorrounding temperature 10°C~30°C[50°F~86°F])
Disconnect the connector and measure the resistance using a tester.
(Refer to the thermistor)
Normal
4.3k ~9.6k
Abnormal
Open or short
CNT(1)-(3)
Normal
App.45
CN3T(1)-(3)
App.1
Abnormal
Open or short
1
2
3
1
2
3
CNT
T
CN3T
Red
Blue
Blue
White
e
v
e
Linear xpansion
valve
Disconnect the connector then measure the resistance alv using a tester.
Refer to the next page for a detail.
Normal
(1)-(5)
White-Red
150
10%
Abnormal
Open or short
(2)-(6)
Yellow-Brown
(3)-(5)
Orange-Red
(4)-(6)
Blue-Brown
1
2
3
4
5
6
LEV
White
Yellow
Orange
Blue
Red
Brown
CN60
Parts name
Check points
Transformer 27VAC
Make sure the proper transformer lead is connected for the proper supply
voltage. See diagram at left.
Measure the supply voltage to the transformer. The supply voltage should be
between 187 and 229 volts if the transformer is connected to a 208 volt power
supply. The reading should be between 207 and 253 volts if connected to a
230 volt power supply.
With the proper supply voltage, the transformer output voltage should be
approximately 27 volts. If no voltage is measured, replace the transformer.
Fan Relays
There are 3 fan relays. One relay for each high, medium
and low speed operation.
The fan relays have a 208/240 V AC coil that is
energized by the circuit board. The relay switches a
24 V AC circuit, which provides the speed signal for the
motor. The relay energized will be determined by which
speed is selected at the controller.
To check operation:
Make sure power to the system is on and the unit is not
in standby mode.
1. Select high, medium or low speed at the controller.
2. At the corresponding relay based on the speed
selected, check the voltage across the relay coil which
is supplied from the circuit board.
3. If 208/230 V is measured, go on to step 4. If no
voltage is measured, replace the circuit board.
4. If there is voltage present, the relay contact should be
closed.
5. To check the contact. Turn power off. Remove the
24 V wires from relay contact.
6. Reapply voltage and select the fan speed. Check the
continuity across the contact. If there is no continuity
across the contact, replace the relay. If there is continu-
ity across the contact, the relay is OK. Refer to the
motor troubleshooting section.
For 208V power supply,
switch the transformer lead
marked 230V with the one
marker 208V. Reattach
wire nut to bare wire.
208/230VAC
27 Volts AC
27 VAC
T2
L2 Blac
k
230 V Whit
e
208 V Orange
208/230 volt supply
from circuit board
Common lead
For 208V power supply,
switch the transformer lead
marked 230V with the one
marker 208V. Reattach
wire nut to bare wire.
208/230VAC
27 Volts AC
24 VAC to motor speeds
27 VAC
9
1
3
5
7
High
Low
Med.
T2
L2 Blac
k
230 V Whit
e
208 V Orang
e
R
R
R
R
R2
R3
7
TROUBLESHOOTING
7-1. How to check the parts
