Simple Check Methods For Inverter / Compressor; Checking For Open Phase; Checking The Resistance Of Transistor Module - Mitsubishi Electric MXZ-18NV Service Manual

(Simple check methods for inverter / compressor)

S t a r t
Check the voltage between
the terminals.
Balanced?
Yes
Proceed to the
compressor check.
A Checking for open phase
Be sure to use the analog tester for measurement.
• With the lead wire disconnected, activate the inverter and check the balance of voltage between terminals.
Operation mode Operational frequency (Hz)
COOL
HEAT
<Operation method>
Perform the test run in the heating mode by using the emergency run
switch on the indoor unit.
<Measure point>
Measure the AC voltages at the following three points on the transistor
module
• BLK - WHT
• BLK - RED
• WHT - RED
<Judgment>
Balanced : Normal
Unbalanced : Faulty (Open phase)
Shut off by overcurrent : Faulty (Short)
NOTE 1 : After the outdoor fan starts running, wait for one minute or more before measuring the voltages.
NOTE 2 : The output voltage values in the above table have the tolerance of ± 20%.
B Checking the resistance of transistor module
• Disconnect the lead wires and check the resistance of terminals at the transistor module.
<Measure points>
Measure the AC voltage at the following six points on the transistor module.
BLK - WHT, WHT - BLK
BLK - RED, RED - BLK
WHT - RED, RED - WHT
<Judgment>
Infinite (Ω) : Normal
Zero to dozens (Ω) : Faulty (Short)
44
Disconnect the compressor lead wire.
Proceed to the A A for checking for open phase.
Check the resistance of
the transistor module
No
Proceed to C C
Zero to
dozens of ohms
Output voltage (V)
58 110
40 70
Proceed to B B for checking the
transistor module.
Infinite
Replace the outdoor controller board.
Replace the transistor module and
outdoor controller board in a set.
Tester indication
BLK-WHT BLK-RED
ACV ACV
300
BLK-WHT BLK-RED
ACV ACV
300
WHT-RED
ACV
Normal
(balanced)
300 300
WHT-RED
ACV
Faulty
(unbalanced)
300 300
Tester indication
Normal
(Infinite)
X1
Faulty
(Zero to dozens of ohms)
X1