48
Packaged and Split Rooftop Ventilator
© 2021 Mitsubishi Electric US, Inc.
Judgment Methods and Possible Failure Mode
Malfunction Mode Judgment Method Remedy
Microcomputer driver
circuit failure
Disconnect the control board connector and connect the check
LED as shown in the gure below.
6
5
4
3
2
1
1 k
LED
Resistance: 0.25W 1kΩ
LED: DC15V 20mA or more
When the main power is turned on, the control board pulse
signals to the LEV’s for 10 seconds
When the drive circuit
has a problem, replace
the control board.
LEV mechanism is
locked
If the LEV is locked, the drive motor runs idle, and makes a small
clicking sound.
When the valve makes a closing and opening sound, the valve
has a problem.
Replace the LEV.
Disconnected or
short-circuited LEV
motor coil.
Measure resistance between the coils (red-white, red-orange,
brown-yellow, brown-blue) using a tester. They are normal if
resistance is 200 ohm ± 10%.
Replace the LEV coils.
Faulty wire
connections in the
connector or faulty
contact.
1. Check for loose pins on the connector and check the colors
of the lead wires visually.
2. Disconnect the control board’s connector and conduct a
continuity check using a tester.
Check the continuity
at the points where an
errors occurs.
Solenoid Valve
Judgement methods and possible failure mode
Solenoid valves are normally closed when de-energized and open when energized. Solenoid valves should make a
clicking noise when coil is energized. If no noise is heard, follow coil test procedure below.
Measure the temperature at the upstream and downstream pipes of the solenoid valve. When the solenoid valve in
ON: There is no temperature dierence. When the solenoid valve is OFF: there is a temperature dierence.
Solenoid valve coil
SV10, SV11
Measure the resistance between the terminals with a tester.
(Surrounding temperature 20ºC [68ºF]
Normal Abnormal
1183 ± 100Ω Open or short
Troubleshooting – Split DX Refrigeration Circuit
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