Hitachi RAF-25NH5 Instructions De Service page 276

When the connectors of the thermistors are disconnected or the thermistors is open or short, LD301A (red) lights and
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LD302A (orange) blinks so that they indicate troubled parts. Combinations of LD301A and LD302A, LD301B and LD302B
are set up for indicating troubled thermistors of A cycle and B cycle each. The correspondences between the number of blink
time and troubled parts are shown as Table 6-3. Look in the table (LD301 and LD302 blink) for troubled parts, and if the
disconnections of them are checked out, they are replaced.
If you can see two or more troubled thermistors in one cycle by the table, a small number of blink takes precedence of others.
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(When the thermistors of A and B cycle are troubled at the same time, LD301A and LD301B light, and LD302A and LD302B
blink.)
The electric expansion valve thermistor is put together with 4 pieces, when replacing the thermistor, replace one set of 4 pieces
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as taking care of positioning. If you donÕt do so, the unit may not operate normally and its cooling and heating performance
may drop.
Be aware that only an open-circuit for OH thermistor has to be checked in 5 minutes after the compressor starts.
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If the unit operates abnormally after replacing the thermistor, replace the control P.W.B. because it malfunctions.
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Table 6-3 LED lighting mode at the thermistors troubled
LED lighting mode
LD301A LD302A
Lights 1 blink OH thermistor A
Lights 2 blinks DEF thermistor A
Lights 3 blinks Outdoor temperature thermistor
Lights 4 blinks Electric expansion value thermistor (thin pipe1) A
Lights 5 blinks Electric expansion value thermistor (thick pipe1) A
Lights 6 blinks Electric expansion value thermistor (thin pipe 2) A
Lights 7 blinks Electric expansion value thermistor (thick pipe 2) A
LD301B LD302B
Lights 1 blink OH thermistor A
Lights 2 blinks DEF thermistor A
Lights 4 blinks Electric expansion value thermistor (thin pipe1) B
Lights 5 blinks Electric expansion value thermistor (thick pipe1) B
Lights 6 blinks Electric expansion value thermistor (thin pipe 2) B
Lights 7 blinks Electric expansion value thermistor (thick pipe 2) B
The OH thermistors are detecting the compressor head temperatures. If the temperature rises over 118¡C, the compressor
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in the cycle will be stopped to protect itself and LD301 will blink 6 times (OH STOP). When the compressor temperature
fells under 105¡C, the compressor will restart. During OH STOP, the fan continues to spin. The other cycles without a
trouble operates normally.
If OH STOP often occurs, the refrigerant may be leaking.
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Troubled thermistor
- 306 -
Judgement
Open Short
0.04V or less 4.96V or more
0.04V or less 4.94V or more
0.04V or less 4.96V or more
0.04V or less 4.94V or more