Mitsubishi Electric CITY MULTI PUHY-400YMF-B Service Handbook page 149

5) Treatment of Fan Motor Related Troubles
Condition
1 It won't run for 20
minutes or longer when
the AK value is 10 %.
(When the MAIN
board's SW1 is set as
shown below, the AK
value is displayed by
the service LED.
• For Variable capacity
unit
SW1 = 0101001000
• For Constant capacity
unit
SW4-2 = ON
SW1 = 0101001000
2 The fan motor's vibra-
tion is great.
Caution
In the PUHY-400/500YMF-B, there are 2 fan motors, but as necessary, the fan motor on the left side when viewed from
the front stops.
When there is a short intermediate period or the indoor unit has a low running capacity, the fan's rotational speed may
fluctuate.
Possible Cause
1) The power supply
voltage is abnormal.
2) Wiring is faulty.
3) The motor is faulty.
4) A fuse (F1, F2, F3) is
defective.
5) The transformer (T01)
is defective.
6) The SCRM is defective.
7) The circuit board is
faulty.
–146–
Check Method and Treatment
If there is an open phase condition before the breaker,
after the breaker or at the power supply terminal blocks
TB1 or TB1A, correct the connections.
If the power supply voltage deviates from the specified
range, connect the specified power supply.
For the following wiring, 1 check the connections, 2 check
the contact at the connectors, 3 check the tightening
torque at parts where screws are tightened, 4 check the
wiring polarity, 5 check for a broken wire and 6 check for
grounding.
Variable capacity unit
TB1 ~ NF ~ TB1A ~ CNTR1 ~ T01 ~ CNTR
TB1A ~ [F1, F2] ~ SCRM ~ CN04 ~ CNMF
CNFC1 ~ CNFC2
CNU ~ SCRM
CNV ~ SCRM
CNW ~ SCRM
SCRM ~ 52F ~ CNO5 ~ CNMF3 ~ MF3
SCRM ~ CNO4 ~ CNMF2 ~ MF2
* Check if the wiring polarity is as shown on the wiring
diagram plate.
Measure the resistance of the motor's coils: 20 ~ 60 Ω
Measure the motor's insulation resistance with a megger:
10 MΩ (DC 500 V) or more
If a fuse is defective, replace it.
Judge that T01 is faulty. Go to "Individual Parts Failure
Judgment Methods."
Judge that the SCRM is faulty. Go to "Individual Parts
Failure Judgment Methods."
If none of the items in 1) to 6) is applicable, and the
trouble reappears even after the power is switched on
again, replace the circuit board using the following
procedure. (When replacing the circuit board, be sure to
connect the connectors and ground wire, etc. securely.)
1 Replace the FANCON board only. If it recovers, the
FANCON board is defective.
2 Replace the FANCON board and replace the MAIN
board. If it recovers, the MAIN board is defective.
3 If the trouble continues even after 1 and 2 above, then
both boards are defective.
(On the constant capacity unit, treat the MAIN board
as the CONT board.)
Constant capacity unit
TB1 ~ F3 ~ T01 ~ CNTR
TB1 ~ F1, F2 ~ SCRM ~ CN04 ~ CNMF ~ MF
CNFC1 ~ CNFC2
CNU ~ SCRM
CNV ~ SCRM
CNW ~ SCRM