Mitsubishi Electric SLH Series Technical & Service Manual page 58

Check of indoor controller board and indoor fan motor
No
Connection is defective.
Check the indoor coil thermistor.
Is the connector CN21 on the
indoor controller board connected?
Yes
No
Measure the resistance
of indoor coil thermistor.
Connection is defective.
Is the resistance 0 (short circuit) or
∞ (open circuit)?
Yes
No
Indoor coil thermistor
is defective.
Operation lamp blinks once in a fixed period.
Error was found in the signal transmitted or
received between the indoor and outdoor units.
Is the connecting wire between
the indoor and outdoor units
connected properly?
Yes
Turn off the power supply and turn it on again to operate the unit in
cooling or heating mode.
Operation lamp blinks once in a
fixed period.
No
Normal
Indoor controller board is defective.
Operation lamp blinks twice in a fixed period.
Check the room temperature thermistor.
Is the connector CN20 on the
indoor controller board connected?
No
Measure the resistance of
room temperature thermistor.
Connection is defective.
Is the resistance 0 (short circuit) or
∞ (open circuit)?
Yes
Room temperature
thermistor is defective.
Turn off the power supply and turn it on again to operate the unit in
cooling mode.
Operation lamp blinks twice in a
fixed period.
No
Normal
Indoor controller board is defective.
Are there any devices emitting
noise near the power supply or
the connecting wire between the
indoor and outdoor units?
Yes
Remove the devices.
Yes
Yes
No
Connection is defective.
Yes
No
Drain sensor is defective.
Yes
58
No
Check the drain sensor thermistor.
Is the connector CN31 on the
indoor controller board connected?
Yes
Measure the resistance
of drain sensor.
Is the resistance 0 (short circuit) or
∞ (open circuit)?
No
To be continued on the next page.