Hitachi RAF-25RPA Service Manual page 62

2. Power circuit for P.W.B.
• The v oltage specification of the power circuit is as follows.
<Check points>
Output Voltage
spec.
12V 11-13V
5V 4.5-6V
B-12V 11-16V
15V 14-17V
35V 33.5-38V
• Check each voltage. If each voltage meets the voltage specification above, the power circuit is normal.
• If any error is found after checking, remove all loads and recheck each voltage.
If no error is found in this step, the power circuit is normal. Check the removed loads.
If any error is found in this step, the power circuit has any failure. Replace the power circuit for P.W.B.
* A short-circuited load may cause an output error not only in the load but also in the others. Be sure to
check all outputs of the loads.
* Be sure to wait 15 minutes or more in order to discharge all the remaining voltage in the circuit to
connect/disconnect the wiring, other wise, the components may be damaged.
• The failures of the loads are as follows.
Possible causes
Failed
output
Reversed connection of the cable.
35V
Electrical part for the indoor unit has
a failure.
Short-circuited reversing valve
DC fan motor error
15V
Main P.W.B. error
Main P.W.B. error
12V, 5V
Main load
MAIN P.W.B.
MAIN P.W.B.
Expansion valve
DC fan motor (CN24)
MAIN P.W.B.
Indoor unit electrical parts
(Terminal C,D)
Reversing valve (CN2)
Measuring points
+ –
R117 ("12V" display) R117 ("0V" display)
R424 ("5V" display) R117 ("0V" display)
L104 ("B-12V" display) R110 ("B-0V" display) LD301 blinks 5 times;
L105 ("15V" display) R117 ("0V" display)
D103 R109 ("0V-35V" display) Indoor unit
("C-35V" display) Terminal D (red line)
Terminal C (blown line)
Criterion
Connect the cable correctly.
Remove the connection cable and measure the
voltage. If the voltage is correct, check the electrical
parts for the indoor unit.
Remove the CN2 and measure the voltage. If the
voltage is correct, check the reversing valve.
Remove the CN24 and measure the voltage.
If the voltage is correct, check the DC fan motor.
Also, check the main P.W.B. 1 A fuse for blow
out in this step.
Check the main P.W.B.
62
Potential failure modes
The unit won't operate
MAIN P.W.B. error
The unit won't operate
MAIN P.W.B. error
Expansion valve error
LD301 blinks 3 times,
Abnormal low speed rotation
won't operate