Trouble Criterion Of Main Parts - Mitsubishi Electric MSH09TW Service Manual

Symptom
Display Abnormal
d d 8 8
Frequency drop by current
protection
(d8)
d d 9 9
Frequency drop by overload
protection
(d9)
Frequency drop by high pres-
d d 7 7
sure protection
(d7)
Frequency drop by defrosting
in cooling
d d 6 6
Frequency drop by discharge
temperature protection
(d6)
d d 3 3
Frequency drop by high pres-
sure switch (63H1) protection
(d3)
d d 1 1
Low discharge temperature
protection
(d1)
Symptom
Display Abnormal
e e 7 7
Defrost thermistor abnormality
(E7)
h h 4 4
Power factor detection abnor-
mality
(h4)

2. Trouble criterion of main parts

MSH09TW MSH09TW -
MSH12TN
MSH12TN -
MSH15TN
MSH15TN -
MSH17TN
MSH17TN -
Part name
Room
Measure the resistance with a tester. (Part temperature 50°F ~ 86°F)
temperature
thermistor(RT11)
Indoor coil
thermistor(RT12)
Measure the resistance with a tester.
Defrost
(Part temperature 14°F ~ 104°F)
thermistor(RT61)
Ambient temper-
ature thermistor
(RT63)
MSH09TW -
U1
MSH12/15/17TN -
U1
only
Measure the resistance between the terminals with a tester.
Compressor(MC)
(Part temperature14°F ~ 104°F)
MUH09TW
MUH12/15/17TN
OPEN 302°F i 9°F
CLOSE
203°F i 18°F
Outdoor unit operates. (The compressor operates at reduced frequency.)
When the outdoor unit input current exceeds 22.5 A, the compressor
operates at reduced frequency.
When the compressor load exceeds the specified value, the compres-
sor operates at reduced frequency.
When indoor pipe temperature exceeds 131°F during heating, the com-
pressor operates at reduced frequency.
When the indoor pipe temperature falls to 42.8°F or below during cool-
ing, the compressor operates at reduced frequency.
When the discharge temperature exceeds 230°F, the compressor oper-
ates at reduced frequency.
When the high pressure exceeds 398 PSIG, the compressor operates
at reduced frequency. In addition, the fan speed changes.
When the state with low discharge temperature of which 122°F in COOL
and 119.3°F or less in HEAT for 20 minutes, the compressor operates
continuously.
When a short or open circuit occurs in the defrost thermistor during
heating
* In this case, the compressor continues to operate.
When the compressor power factor cannot be detected
* In this case, the compressor keeps running.
MUH09TW MUH09TW -
U1
MUH12TN
MUH12TN -
U1
MUH15TN
MUH15TN -
U1
MUH17TN
MUH17TN -
U1
Check method and criterion
Normal
8kΩ ~ 20kΩ
Normal
5kΩ ~ 60kΩ
MUH09 MUH12/15
C-R 0.7~0.9Ω 1.4~1.9Ω
1.3~1.6Ω 2.4~3.0Ω
C-S
Detecting method
Outdoor unit operates.
Detecting method
MUH12TN -
U1
U2
MUH15TN -
U1 U2
U1
U1
Abnormal
Open or short-circuit
Abnormal
Open or short-circuit
Normal
MUH17
1.4~1.8Ω
2.3~2.9Ω
80
Check points
These symptoms do not mean any
abnormality of the product, but check the
following points.
• Air filter clogging.
• Amount of gas.
• Short cycle of indoor/outdoor air flow.
• Amount of gas.
• Outdoor unit air passage.
Check the amount of gas.
• Replace the outdoor controller board.
• Check the contact of LEV board connec-
tors.
Check points
• Defrost thermistor characteristic.
• Contact of P. C. board connectors.
• Compressor wiring.
Abnormal
Open or
short-circuit
Figure
WHT
P
RED BLK