Troubleshooting By Inferior Phenomena - Mitsubishi Electric EHST20C-VM6HB Service Manual

10-5. Troubleshooting by inferior phenomena

No. Fault symptom
1. There is no power supply to main
1 Main controller display
is blank.
. Power is supplied to main controller,
1. "Please Wait" is displayed for up to 6
 "Please Wait" remains
displayed on the main
. Communication failure between the main
controller.
. Communication failure between FTC4
The main controller operations do not work
 The main screen
appears with a press for a while after the settings are changed in
of the "ON" button, but the service menu. This is because the system
takes time to apply the changes.
disappears in a second.
LED2 on FTC4 is off. When LED1 on FTC4 is also off. (See 6.
4
(See 6. WIRING WIRING DIAGRAM.)
<FTC4 powered via outdoor unit.>
DIAGRAM.)
1. The outdoor unit is not supplied at the
. Defective outdoor controller circuit board.
.
4. FTC4 failure.
5.
OCH531
Possible cause
controller.
however, the display on the main
controller does not appear.
minutes.
controller and FTC4.
and outdoor unit.
rated voltage.
FTC4 is not supplied with 220 to 240V
AC.
Faulty connector wiring.
Explanation - Solution
1. Check LED2 on FTC4. (See 6. WIRING DIAGRAM.)
(i) When LED is lit.
Check for damage or contact failure of the main controller wiring.
(ii) When LED2 is blinking.
Refer to No. 5 below.
(iii) When LED is not lit.
Refer to No. 4 below.
Check the following:
.
• Disconnection between the main controller cable and the FTC4 control board
• Failure of the main controller if "Please Wait" is not displayed.
• Refer to No. 2 below if "Please Wait" is displayed.
1. Normal operation.
, . Main controller start up checks/procedure.
(i) If "0%" or "50-99%" is displayed below "Please Wait" there is a
communication error between the main controller and the FTC4 control
board.
• Check wiring connections on the main controller.
• Replace the main controller or the FTC4 control board.
(ii) If "1-49%" is displayed there is a communication error between the outdoor
unit's and FTC4's control boards.
• Check the wiring connections on the outdoor unit control board and the FTC4
control board.
(Ensure S1 and S2 are not cross-wired and S3 is securely wired with no
damage. (See 7. FIELD WIRING.)
• Replace the outdoor unit's and/or the FTC4's control boards.
Normal operation.
The indoor unit is applying updated settings made in the service menu. Normal
operation will start shortly.
1. Check the voltage across the terminals L and N or L3 and N on the outdoor
power board. (See 7. FIELD WIRING.)
• When the voltage is not 220 to 240V AC, check wiring of the outdoor unit and
of the breaker.
• When the voltage is at 220 to 240V AC, go to "2." below.
. Check the voltage across the outdoor unit terminals S1 and S2. (See 7. FIELD
WIRING.)
• When the voltage is not 220 to 240V AC, check the fuse on the outdoor
control board and check for faulty wiring.
• When the voltage is 220 to 240V AC, go to "3." below.
. Check the voltage across the indoor unit terminals S1 and S2. (See 7. FIELD
WIRING.)
• When the voltage is not 220 to 240V AC, check FTC4-outdoor unit wiring for
faults.
• When the voltage is 220 to 240V AC, go to "4." below.
4. Check the FTC4 control board.
• Check the fuse on FTC4 control board.
• Check for faulty wiring.
• If no problem found with the wiring, the FTC4 control board is faulty.
Check the connector wiring.
5.
• When the connectors are wired incorrectly, re-wire the connectors referring to
below. (See 7. FIELD WIRING.)
L
N
FTC4 powered
Black
CN01
via outdoor unit
S1
Cylinder unit
S2
control board
S3
60