Mitsubishi MSC-GA20VB Service Manual download pdf (Page 28)

How to check mis-wiring and serial signal error

Serial signal error is indicated.

(0.5-sec. ON, 0.5-sec. OFF)

1. Turn OFF the power supply(indoor/outdoor unit) and disconnect indoor and outdoor connecting wire on indoor side.

2. Short-circuit between indoor terminal block and .

3. Turn ON the power supply

(indoor unit) and press once EMERGENCY OPERATION switch.

During EMERGENCY OPERATION,

is there 10V DC between both ends

of R601?

(By tester, the stylus is between 5 ~10V)

Start

Turn OFF the power supply(indoor/outdoor unit).

Is there 20V DC between both ends of

R132 on indoor electronic control P.C.

board ?

( By tester, the stylus is between 0 ~ 20V. )

•Turn OFF the power supply(indoor unit).

•Connect indoor and outdoor connecting wire.

Is the outdoor unit "MUH" or “MXZ” type?

•Turn ON the power supply(indoor/outdoor unit).

•Press once EMERGENCY OPERATION switch.

•3 min. later, check the self-check result

displayed on OPERATION INDICATOR

lamp on indoor unit. 2

Is this mis-wiring, poor contact,

or disconnection of wire?

Correct them.

Replace the indoor electronic

control P.C. board.

Turn ON the power supply(outdoor unit).

Is there 230V AC between outdoor terminal

block (TB1)?

Check the outdoor power supply,

power supply cord and

connection.

Yes

Turn ON the power supply(indoor unit).

Replace the deicer P.C. board.

Yes

Correct the wiring between

CN730 on the deicer P.C. board

and outdoor terminal block.

Replace the deicer P.C. board.

Yes

Set the switch(SW2- ) on the indoor electronic

control P.C. board to MU or MUX type. 1

Yes

Does the unit operate?

Yes

Refer to the

"Instruction of

troubleshooting."

2 Short circuit of JPG and JPS on the indoor electronic control

P.C. board enables self-check to be displayed in 3 seconds.

1 Set the switch(SW2- ) on indoor electronic control P.C. board to

MU or MUX type, when the outdoor unit is MU or MUX type.

If the setting is MUH or MXZ type, the unit does not work.

Is there 5V DC between J205 + –J101 - on the deicer P.C. board?

Refer to outdoor unit service manual.

When OPERATION INDICATOR lamp flashes 0.5-second intervals or 1-time.

Outdoor unit does not operate.

MUH (Except MUH-GE50VB), MXZ

OBH529A

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Mitsubishi MSC-GA20VB Service Manual Page 28

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