Mitsubishi Electronics Understanding Mis Wiring in Mitsubishi Air Conditioners: Troubleshooting Guide

When POWER lamp flashes ON and OFF in every 0.5-second.

Outdoor unit does not operate.

D How to check mis-wiring and serial signal error

Turn OFF the power supply.

Is there rated voltage of

No

Check the power

230V AC in the power

supply.

supply?

Yes

Turn ON the power supply.

No

Is there 230V AC between

Check the wiring.

outdoor terminal block S1 and

S2?

Yes

Press EMERGENCY OPERATION switch.

Does POWER lamp light up?

<Confirmation of the power to the indoor unit>

No

Yes

Is there any mis-wiring,

Is the self-check of the indoor unit displayed 6

No

poor contact, or wire

Yes

Make them sure.

minutes after?

disconnection of the

indoor/outdoor

Yes

connecting wire?

Serial signal error display

No

POWER lamp

blinks quickly.

A

Turn OFF the power supply.

Check once more if the indoor/outdoor

connecting wire is not mis-wiring.

B

Short-circuit outdoor terminal block S2 and

W1. Mis-wiring may damage indoor electronic control

S3.

P.C. board during the operation.

W1

Be sure to confirm the wiring is correct before the

operation starts.

Turn ON the power supply of the outdoor unit.

In 3 minutes after turning ON the

power supply of the outdoor unit, does

the LED on the inverter P.C. board

Inverter P.C.board

repeat quick blinking "3.6-second-OFF

No

Replace the inverter

and 0.8-second-ON"?

(Parts side)

P.C. board.

Be sure to check above in 3 minutes

(Lighting)

W2

after turning ON. After 3 minutes, LED

blinks 6 times. When the inverter P.C.

W2 Be careful to the residual

LED

board is normal, LED also blinks 6

voltage of smoothing capacitor.

times after 3 minutes.

Blinking

Yes

A

Remove the short-circuit between

Is there any error of the

·Turn OFF inverter-controlled lighting

outdoor terminal block S2 and S3.

indoor/outdoor connecting wire,

Yes

Replace the

equipment.

Is there amplitude of 10 to 20V DC

such as the damage of the wire,

indoor/outdoor

·Turn OFF the power supply and then

between outdoor terminal block S2

No

intermediate connection, poor

connecting.

turn ON again.

and S3? <Confirmation of serial

contact to the terminal block?

signal>

· Press EMERGENCYOPERATION

switch.

Yes

No

· Reinstall

Is there any error of the

either the

Is there 230V AC between outdoor

indoor/outdoor connecting wire,

Yes

Replace the

unit or the

terminal block S1 and S2?

such as the damage of the wire,

indoor/outdoor

Is serial signal

No

light each

<Confirmation of power voltage>

No intermediate connection, poor

connecting.

other away.

error indicated

Yes

contact to the terminal block?

6 minutes later?

·Attach a filter

on receiving

Replace the indoor electronic control P.C. board.

section of

Yes

the indoor

Be sure to release the failure-mode

unit.

recall function after checking.

B

As for outdoor unit MUZ type,refer to service manual OB372.

As for outdoor unit MXZ type,refer to service manual OB377.

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