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Hitachi RAS-18YH4 Service Manual
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Hitachi RAS-18YH4 Service Manual

Room air conditioner
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See also: Operating Manual

SERVICE MANUAL

TECHNICAL INFORMATION

FOR SERVICE PERSONNEL ONLY
SPECIFICATIONS
TYPE
MODEL
POWER SOURCE
TOTAL INPUT
TOTAL AMPERES
COOLING
CAPACITY
TOTAL INPUT
TOTAL AMPERES
HEATING
CAPACITY
DIMENSIONS
(mm)
NET WEIGHT
SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT
DECEMBER 2004 Hitachi Household Appliance (Wuhu) Co.,Ltd.
RAS-18YH4
RAC-18YH4
(W)
(A)
(kW)
(B.T.U./h)
(W)
(A)
(kW)
(B.T.U./h)
W
H
D
(kg)

ROOM AIR CONDITIONER

INDOOR UNIT + OUTDOOR UNIT
AW
RAS-18YH4 /
RAC-18YH4
REFER TO THE FOUNDATION MANUAL
SPECIFICATIONS .............................. 4
HOW TO USE ................................ 5
MAIN PARTS COMPONENT .................... 17
WIRING DIAGRAM ............................ 19
WIRING DIAGRAM OF THE PRINTED WIRING BOARD .. 20
BLOCK DIAGRAM.............................. 27
BASIC MODE .................................. 29
PARTS LIST AND DIAGRAM .................. 98
DC INVERTER (WALL TYPE)
INDOOR UNIT
RAS-18YH4
1 PHASE, 50Hz, 230V
550 (155 - 1,010)
2.00 (0.90 - 2.50)
6,820 (3,070 - 8,530)
580 (115 - 970)
2.50 (0.90 - 3.20)
8,530 (3,070 - 10,920)
780
280
(+5)
※
205
9.5
NO. 0004E
CONTENTS
........................ 70
RAC-18YH4
2.81
2.81
750 (+91)
548
(+47)
288
35
After installation
※
※
※

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Summary of Contents for Hitachi RAS-18YH4

  • Page 1: Table Of Contents

    8,530 (3,070 - 10,920) 750 (+91) ※ DIMENSIONS (mm) (+5) ※ (+47) ※ NET WEIGHT (kg) After installation ※ SPECIFICATIONS AND PARTS ARE SUBJECT TO CHANGE FOR IMPROVEMENT ROOM AIR CONDITIONER INDOOR UNIT + OUTDOOR UNIT DECEMBER 2004 Hitachi Household Appliance (Wuhu) Co.,Ltd.
  • Page 2 SAFETY DURING REPAIR WORK 1. In order to disassemble and repair the unit in question, be sure to disconnect the power cord plug from the power outlet before starting the work. 2. If it is necessary to replace any parts, they should be replaced with respective genuine parts for the unit, and the replacement must be effected in correct manner according to the instructions in the Service Manual of the unit.
  • Page 3 WORKING STANDARDS FOR PREVENTING BREAKAGE OF SEMICONDUCTORS 1. Scope The standards provide for items to be generally observed in carrying and handling semiconductors in relative manufactures during maintenance and handling thereof. (They apply the same to handling of abnormal goods such as rejected goods being returned.) 2.
  • Page 4 (6) Use a three wire type soldering iron including a grounding wire. Metal plate (of Al. stainless steel, etc.) Bare copper wire (for body earth) Working table Resistor 1M (1/2W) Staple Earth wirte Fig.3 Grounding of the working table soldering iron Grounding wire Screw stop at the screwed part using a rag plate...
  • Page 5 CAUTION In quiet operation or stopping the running, slight flowing noise of refrigerant in the refrigerating cycle is heard occasionally, but this noise is not abnormal for the operation. When it thunders near by, it is recommend to stop the operation and to disconnect the power cord plug from the power outlet for safety.

  • Page 6: Specifications

    SPECIFICATIONS MODEL RAS-18YH4 RAC-18YH4 FAN MOTOR 40 W PWM DC35V FAN MOTOR CAPACITOR FAN MOTOR PROTECTOR COMPRESSOR — ASC092SD-A8JT1 COMPRESSOR MOTOR CAPACITOR OVERLOAD PROTECTOR OVERHEAT PROTECTOR FUSE (for MICROPROCESSOR) 3.0A POWER RELAY POWER SWITCH TEMPORARY SWITCH SERVICE SWITCH TRANSFORMER VARISTOR...
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  • Page 17: Construction And Dimensional Diagram

    CONSTRUCTION AND DIMENSIONAL DIAGRAM MODEL RAS-18YH4 INDOOR UNIT Unit : mm Service space Top air suction grill Mounting plate Front panel Cabinet Discharge grill Horizontal air diflector (190) Drain When piping is drawn from the left side, exchange the drain hose for the drain cap 17.5...
  • Page 18 MODEL RAC-18YH4 OUTDOOR UNIT Unit : mm (19.5) (26) 27.5 Handle Air outlet Air suction Handle Rear side Air suction Holed for anchor bolt (2-φ12×16 slots for φ8.0 bolt) Notch for anchor bolt (for 2-φ8.0 bolt) Fixing hole Drain hole Drain hole Service space More than...

  • Page 19: Main Parts Component

    MAIN PARTS COMPONENT THERMOSTAT Thermostat Specifications MODEL RAS-18YH4 THERMOSTAT MODEL OPERATION MODE COOL HEAT 16.7 (62.1) 18.7 (65.7) INDICATION 16.0 (60.8) 19.3 (66.7) TEMPERATURE 24.7 (76.5) 26.7 (80.1) INDICATION ˚C ( ˚F) 24.0 (75.2) 27.3 (81.1) 32.7 (90.9) 34.7 (94.5) INDICATION 32.0 (89.6)
  • Page 20 COMPRESSOR MOTOR Compressor Motor Specifications MODEL RAC-18YH4 ITEM COMPRESSOR TYPE ASC092SD-A8JT1 POWER SOURCE DC 220 - 350 V OUTPUT 750W (U ) WHITE WINDING (W ) (V ) YELLOW 20 ˚C 2M = 1.15 RESISTANCE (Ω ) 75 ˚C 2M = 1.40 YELLOW WHITE COMPRESSOR...

  • Page 21: Wiring Diagram

    WIRING DIAGRAM MODEL RAS-18YH4 / RAC-18YH4 CAUTION The marked parts are very important ones for safety. – 19 –...
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  • Page 23 MODEL RAS-18YH4 – 21 –...
  • Page 24 MODEL RAC-18YH4 Ｈ８ ／ ３ ０ ３ ９ （ＡＸ−８ Ｔ １ ０） – 23 –...

  • Page 25: Printed Wiring Board Location Diagram

    PRINTED WIRING BOARD LOCATION DIAGRAM MODEL RAS-18YH4 MAIN P.W. B. MARKING ON P.W. B. COMPONENT SIDE SOLDERING SIDE – 24 –...
  • Page 26 MODEL RAS-18YH4 RECEIVING P.W. B. MARKING ON P.W. B. COMPONENT SIDE SOLDERING SIDE MODEL RAC-18YH4 PO WER P.W. B. MARKING ON P.W. B. COMPONENT SIDE – 25 –...
  • Page 27 MODEL RAC-18YH4 MAIN P.W. B. MARKING ON P.W. B. COMPONENT SIDE SOLDERING SIDE – 26 –...

  • Page 28: Block Diagram

    BLOCK DIAGRAM MODEL RAS-18YH4 RAC-18YH4 INDOOR UNIT OUTDOOR UNIT Outdoor DC fan motor Power source 1ø 50Hz 230V HARMONICS POWER POWER RELAY IMPROVEMENT SWITCH RECTIFIER CIRCUIT Inrush current DC compressor Protection circuit motor Rotor magnetic pole position detection circuit Wireless receive...

  • Page 29: Basic Mode

    BASIC MODE MODEL RAS-18YH4 – 29 –...
  • Page 30 Table 1 Mode data file RAS-18YH4 LABEL NAME VALUE –1 3500 min WMAX –1 3500 min WMAX2 2950 min –1 WSTD –1 2900 min WBEMAX –1 3300 min CMAX 3300 min –1 CMAX2 2500 min –1 CSTD –1 2500 min...
  • Page 31 Table 1 Thermo judgment Item Temperature Thermo judgment (ON) 30°C Room CLMXTP temperature Thermo judgment (OFF) 32°C Thermo judgment (ON) 32°C Outdoor temperature Thermo judgment (OFF) 33°C Table 2 Compressor rpm Temperature Calculated difference compressor rpm (with shift value) 1.66°C 2500 min –1 button...
  • Page 32 Cooling Sleep Operation Dehumidifying Operation Room temperature 7 hr 1 hr Set to 7 hours Sleep button Operation lamp Timer lamp Remote control (Sleep) ON See basic Start Stop button operation Indoor fan Sleep Lo Outdoor fan Horizontal air Shut deflector Horizontal Facing down...
  • Page 33 Table 3 Compressor rpm Basic Heating Operation Temperature Calculated difference compressor rpm (with shift value) 1900 min –1 1.66°C 2400 min –1 2.00°C Heating set temperature –1 2900 min 2.33°C (remote control set temperature (+)) –1 3400 min 2.66°C 3900 min –1 3.00°C Dash period...
  • Page 34 Heating Sleep Operation Reversing Valve Defrosting Preheating released Sleep button Reversing valve (cooling "on" model　 2min. 30sec. Sleep Lo Notes: (1) The defrosting inhibit period is set as shown in the diagram below. When defrosting has finished once, the inhibit period is newly set, based on the outdoor temperature when the compressor was started. During this period, the defrost signal is not accepted.

  • Page 35: Refrigerating Cycle Diagram

    REFRIGERATING CYCLE DIAGRAM MODEL RAS-18YH4 RAC-18YH4 – 38 –...

  • Page 36: Description Of Main Circuit Operation

    DESCRIPTION OF MAIN CIRCUIT OPERATION MODEL RAS-18YH4 1. Reset Circuit NORMAL : HI RESET : LO Microcomputer R552 IC521 Fig. 1-1 Power "OFF" Power "ON" Voltage 5.0V Voltage supply to pin 2 of IC521 Reset enter at 4.2V Reset release at 4.4V Voltage 5.0V...
  • Page 37 2. Receiver Circuit Q141 R212 L201 R141 ZD141 C212 C211 RECEIVER I/P R211 R611 C611 Microcomputer Fig.2-1 IRR (light receiver unit) receives the infrared signal from the wireless remote controller. The receiver amplifie and shapes the signal and outputs it. 3.
  • Page 38 4. Auto Sweep Motor Circuit Auto sweep motor for horizontal air defectors IC711 Microcomputer Rotor Fig.4-1 Fig. 4-1 shows the Auto sweep motor drive circuit; the signals shown in Fig.4-2 are output from pin 15 - 18 of microcomputer. Step width : 10ms Micro computer pins Horizontal air deflectors Fig.4-2 Microcomputer Output Signals...
  • Page 39 5. Initial Setting Circuit (IC401) • When power is supplied, the microcomputer reads the data in IC401 or IC402 (E PROM) and sets the preheating activation value and the rating and maximum speed of the compressor, etc. to their initial values. •...
  • Page 40 7. Fan Motor Drive Circuit CN10 Micro computer DC fan motor output Fan motor R751 C751 DC fan motor Speed feedback R631 C631 Fig. 7-1 Voltage at point A Waveform T1 = Low speed T2 = High speed Voltage at point B Waveform Voltage at point C Waveform...
  • Page 41 MODEL RAC-18YH4 1. The electrical parts for the outdoor unit is composed of two P.W.B (a power P.W.B. and main P.W.B.) and a harmonics improvement circuit as shown in Fig. 1-1. • MAIN P.W.B. This P.W.B. is equipped with the rectification diode, DC fan motor control circuit and the circuits around the micro computer which take various controls.
  • Page 42 2. Power circuit This circuit is to convert the power from AC which is provided from the terminal A and B to DC voltage And produces an AC current which does not exceed the harmonic amplitude limit of the IEC61000-3-2. When the compressor is stopped, the AC voltage becomes about 300 V and while the compressor operates, it is about 280 V.
  • Page 43 (3) C021 and C022 This smoothes the voltage rectified for operating the compressor. When the input voltage is taken for the sine wave as shown in the top of Fig. 2-4, it is rectified by the DB2 and becomes the waveform as shown in the middle of Fig.
  • Page 44 3. Indoor/Outdoor Interface Circuit The interface circuit superimposes an interface signal on the DC 35V line to perform communications between indoor and outdoor units. This circuit consists of a transmitting circuit which superimposes an interface signal transmit from the microcomputer on the DC 35V line and a circuit which detects the interface signal on the DC 35V line.
  • Page 45 Fig. 3-1 shows the interface circuit used for the indoor and outdoor microcomputers to communicate with each other. Fig. 3-1 – 48 –...
  • Page 46 Outdoor microcomputer Pin !1 Pin ^8 Indoor microcomputer Pin %0 Pin $9 35V DC line 33ms. 100ms. 1 frame Leader Fig. 3-2 Voltages Waveforms of Indoor / Outdoor Microcomputers (Outdoor to Indoor Communications) Outdoor microcomputer Pin !1 Pin ^8 Indoor microcomputer Pin %0 Pin $9 35V DC line 4.95ms.
  • Page 47 ∼ ∼ ∼ ∼ ∼ ∼ – 50 –...
  • Page 48 Compressor minimum rotation speed(4 MSB) Compressor minimum rotation speed(3) Compressor minimum rotation speed(2) Compressor minimum rotation speed(1) Compressor minimum rotation speed(0 LSB) OVL up Fan-7-step request 15/20(A) Actual compressor rotation speed(5 MSB) Compressor command speed(7 MSB) Actual compressor rotation speed(4) Compressor command speed(6) Actual compressor rotation speed(3) Compressor command speed(5)
  • Page 49 4. IPM (Intelligent Power Module) • Fig.4-1 shows the intelligent power module and its peripheral circuit. The three transistors on the positive e side are called the upper arm, and the three transistors on the negative d side, the lower arm. Fig.
  • Page 50 Intelligent power module switches power supply current according to position of the compressor motor rotor. The switching order is as shown in Fig. 4-2. – At point E : U is ON, V is ON (circuit in Fig. 4-1) – At point F : U is chopped (OFF), V is ON (circuit in Fig.
  • Page 51 – Fig. 4-4 Power module circuit (U is OFF, V is ON) – Since current flows at point B only when U transistor and V transistor is ON, the current waveform at point B becomes intermittent waveform as shown in Fig.4-3. Since current at point B is approximately proportional to the input current of the air conditioner, input current is controlled by using DC current (Id) detection resistor.
  • Page 52 • IPM drive circuit The inverter driving device (IGBT) and the drive circuit are built in the IPM. The IPM receives the signal from the microcomputer and convert it to 0 – 15 V signal to drive the IGBT. When the unit operates at low speed, a chopper signal is emitted from the micro computer as shown in Fig.
  • Page 53 5. Power Circuit for P.W.B. • Fig. 5-1 shows the power circuit for P.W.B. • In the power circuit for P.W.B., power supply for microcomputer, peripheral circuits, and IPM driver circuit and, as well as DC 35V, are produced by switching power circuit. •...
  • Page 54 • The voltage specification of the power circuit is as follows. <Check points> Output Voltage Main load Measuring points Potential failure modes spec. – 11-13V MAIN P.W.B. (CN3, CN4) R701 (“12V” display) R006 (“0V” display) The unit won’t operate C21 (“12V” display) J27, J30 MAIN P.W.B.
  • Page 55 6. Microcpomputer's Peripheral Circuits 6-1. Overload control circuit (OVL control circuit) Overload control is to decrease the speed of the compressor and reduce the load when the load on the air conditioner increases to an overload state, in order to protect the compressor, electronic components and power breaker.
  • Page 56 Detection DC Current Resistor Direct Current R003 R004 Q501 R513 Power P.W.B. R514 R906 Main P.W.B. R613 Microcomputer R612 R248 − R245 R222 CN4B CN4A C009 R005 D001 R287 D208 Reset output − Reset R288 R252 0V 0V 0V Main P.W.B. Fig.
  • Page 57 R003,R004,R608,R613, detect the DC voltage at the power circuit. The microcomputer receives a DC voltage and applies correction to the overload set value so the DC current will be low when the DC voltage is high. (Since the load level is indicated by the DC voltage multiplied by DC current, R247, R248, R249 are provided to perform the same overload judgement even when the voltage varies.) DC voltage : Low DC current : High...
  • Page 58 6-2. Reset Circuit MAIN P.W.B. D208 R287 Microcomputer RESET OUT. − R252 RESET C204 IC5(1/2) R288 0V 0V 0V 0V Fig. 6-7 The reset circuit initializes the microcomputer program when Power is “ON” from “OFF”. Low voltage at pin 48 resets the microcomputer , and HI activates the microcomputer. Fig.
  • Page 59 7. Temperature Detection Circuit MAIN P.W.B. O.H. thermistor R304 R301 DEF. thermistor Microcomputer R305 C302 R302 Outdoor temperature thermistor CN10 R306 Outdoor temperature C302 R303 Fig. 7-1 The Over heat thermistor circuit detects the temperature at the surface of the compressor head, the Defrost. thermistor circuit detects the defrosting operation temperature.
  • Page 60 8. Reversing valve control circuit C-35V Power P.W.B. MAIN P.W.B. Reversing valve R701 D701 PQ701 Microcomputer CN4A CN4B Q701 R705 DC voltmeter R706 or multimeter D-0V Fig. 8-1 Reversing valve control circuit will switch reversing valve ON/OFF(cooling ON) according to instruction from indoor microcomputer depending on the operation condition shows in Table 8-1.
  • Page 61 9. Electric expansion valve control circuit POWER P.W.B. MAIN P.W.B. B-12V B-12V CN15 B-12V R403 R404 R401 Microcomputer PQ401 R293 Valve4 PQ402 R294 Valve3 Electric PQ403 R295 Valve2 expansion valve PQ404 R296 Valve1 CN4B CN4A 12 13 C401 B-0V Fig. 9-1 •...
  • Page 62 10. Outdoor DC Fan Motor control circuit This model uses DC Fan Motor which has a controller circuit built in the Motor. This DC Fan Motor will rotate by control voltage apply to Vsp input. (Voltage range: 1.7 to 7V DC) Vsp high : Faster ;...
  • Page 63 < Reference > When operation stop with LD301 blinks 12 times, it may be caused by faulty DC fan motor. In this case, please check CN6 and CN12 connection first. It makes Fan Motor Lock also if those connectors are in misconnection. DC Fan Motor has broken invites 1A Fuse burned.

  • Page 64: Service Call Q & A

    SERVICE CALL Q & A MODEL RAS-18YH4 RAC-18YH4 COOLING MODE The compressor has Check if the indoor heat If the air conditioner operates stopped suddenly during exchanger is frosted. in cooling mode when it is cooling operation. Wait for 3-4 minutes cold, the evaporator may get until it is defrosted.
  • Page 65 AUTO FRESH DEFROSTING Auto Fresh Defrosting is carried out : the After the ON/OFF button is pressed system checks the outdoor heat exchanger to stop heating, the outdoor unit is and defrosts it as necessary before stopping still working with the OPERATION operation.
  • Page 66 When the “Sleep” timer is set during (1) The temperature arrives at the preset indoor operation, temperature and the air conditioner unit is (1) The indoor fan won’t rotate. temporarily stopped. Within about 3 minutes, (No air comes from the unit) the fan starts rotation.

  • Page 67: Trouble Shooting

    TROUBLE SHOOTING RAC-18YH4 PRECAUTIONS FOR CHECKING Power inlet WARNING Remember that voltage of 175 V is applied to the 0V line on the P.W.B. or the like as shown in the right diagram. Always keep your hands and metallic things away WARNING from the cabinet.
  • Page 68 DISCHARGE, PROCEDURE AND POWER SHUT OFF METHOD FOR POWER CIRCUIT WARNING Caution • Voltage of about 350 V is charged between the terminal of smoothing capacitors (400µF x 2). • During continuity check for each circuit part of the outdoor unit, be sure to discharge the smoothing capacitors.
  • Page 69 STRUCTURE OF AN INDOOR UNIT ELECTRIC PARTS RAS-18YH4 ELEC. COVER FIXTURE SCREW FIXTURE SCREW Removing electrical parts When installing the parts, use 1. Remove the electrical parts cover. caution not to pinch any code 2. Remove the connectors from the CN1 (heat exchange between the part and cabinet.
  • Page 70 Other Cautions (1) Cautions concerning ICP (IC Protector) 1. Use due caution for short circuit in servicing. Short circuit will open the ICP immediately. 2. When the ICP opens, remove the cause of this phenomenon and replace the ICP. If the remedy is improper, the ICP may open again. 35V line ICP2 Indoor unit fan motor...
  • Page 71 THE SUPPORT FUNCTION OF FAILURE DIAGNOSIS Function Name Description Self-diagnosis indication function • The “timer lamp” indicates a mode of failure detected <Indicating a failure on the indoor on the indoor or outdoor unit side by blinking unit side> frequency. •...
  • Page 72 TROUBLESHOOTING WHEN TIMER LAMP BLINKS. MODEL RAS-18YH4 Perform troubleshooting according to the number of times the indoor timer lamp and outdoor LD301 blink. SELF-DIAGNOSIS LIGHTING MODE MODEL RAS-18YH4 Blinking of Timer lamp Reason for indication Possible cause Reversing valve defective...
  • Page 73 SELF-DIAGNOSIS LIGHTING MODE MODEL RAC-18YH4 INTELLIGENT POWER MODULE LD301 SELF DIAGNOSIS LAMPS LD302 SERVICE SWITCH LD303 – 76 –...
  • Page 74 OUTDOOR UNIT Remove the compressor connector. INTELLIGENT POWER MODULE LD301 SELF DIAGNOSIS LAMPS LD302 LD303 SERVICE SWITCH • Check the drive If your first attempt With the unit set in the operating circuit (IMP) using fails, wait 3 minutes state, press the start/stop the PRD checker.
  • Page 75 CHECKING THE INDOOR/OUTDOOR UNIT ELECTRICALPARTS AND REFRIGERATING Trouble shoot according to the Is the indoor unit "timer lamp" blinking? self-diagnosis lighting mode. Open the indoor unit and check the voltage Run the unit using the following remote controller settings: between pins Nos.1 and 3 of CN3 on the In the cooling season, set the temperature to 16℃...
  • Page 76 CHECKING THE INDOOR UNIT ELECTRICAL PARTS 1. Power does not come on (no operation) Is AC230V being generated between Is AC230V being generated at AC Check AC outlet and breaker, and terminals A and B on the indoor unit outlet? repair any defective part.
  • Page 77 2. Indoor fan does not operate (others are normal) The microcomputer fan PWM Can the fan be stopped by remote Replace the microcomputer . output (at pin 24 ) is 1 - 5V. control? Replace the fan motor . Replace the microcomputer . Perform final operation check.
  • Page 78 4. Check the control P.W.B. (power circuit) Is 35V or 20V being output Check to see if the connection cables are at pin 5 relative to 0V at disconnected or reversed. pin 3 of CN3? If normal, check the outdoor unit P.W.B. Is 12V or 7V being output Is ICP1 normal? at (+) relative to 0V at (-) of...

  • Page 79: Checking The Remote Controller

    CHECKING THE REMOTE CONTROLLER Is battery polarity correct? Install the battery in the correct polarity. Is the battery check sign + – Replace the battery. flashing? Turn on an AM radio, bring the remote control switch within 15 cm of the radio, and press the ON/OFF button.
  • Page 80 WARNING PRECAUTIONS FOR SERVICING Be sure that the power switch is turned off or the power cable is disconnected before servicing. Removing the P.W.B.s. System Configuration of Outdoor Unit Electrical Parts The outdoor unit electrical parts consist of two P.W.B.s as shown in the figure. <Control P.W.B.
  • Page 81 [C. Power Factor Improvement capacitor] Designed to improve power factor. To replace the capacitor, remove the power P.W.B. and then: 1. Remove two screws fastening the capacitor seat. 2. Slide the capacitor seat in the direction of the arrow. Sliding Direction –...
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  • Page 89 (JUDGING BETWEEN GAS LEAKAGE AND CHECKING THE REFRIGERATING CYCLE COMPRESSOR DEFECTIVE) 1. Troubleshooting procedure (No operation, No heating, No cooling) Lighting mode Blinks Blinks Blinks Blinks Blinks Blinks Connect U,V,W phase leads to the Self- 2 times 3 times 4 times 5 times 6 times 8times...

  • Page 90: How To Operate The Outdoor Unit Independently

    HOW TO OPERATE USING THE SERVICE SWITCH THE OUTDOOR UNIT MODEL RAC -18YH4 1. Turn off the power switch. 2. Remove the electrical box cover. 3. Turn on the power switch 4. After waiting for 30 seconds, push the service switch for a second. LD303 (red) will light and the unit will operate in the forced cooling mode at this time.
  • Page 91 IPM (Intelligent Power Module) DIAGNOSIS SSM1001MA Circuit diagram of Collector the device Emitter Circuit diagram of the module Terminals symbol mark of the module See next page for measuring value using multimeter – 94 –...
  • Page 92 To find the malfunction either the power supply of power P.W.B. or internal IC, please follow the – 95 –...

  • Page 93: Procedure For Disassembly And Reassembly

    Procedure for Disassembly and Reassembly 〈INDOOR UNIT〉 MODEL RAS-18YH4 1. Front Panel 3. Main P.W.B. and Reception/Indication (1)Pull up the washable panel by holding it at both P.W.B. lower sides with both hands. (1)Remove each connector from the lead wire.
  • Page 94 4. Tangential air flow fan and fan motor 〈OUTDOOR UNIT〉 MODEL RAC-18YH4 (1)Remove two screws locking the drain pan. 1. Electrical parts (2)Press to lower the hook at the center of the (1)Remove the service value cover lock screws unit a little and pull the claw forward to remove and lower the cover to remove it.

  • Page 95: Parts List And Diagram

    PARTS LIST AND DIAGRAM INDOOR UNIT MODEL: RAS-18YH4 15 16 – 98 –...
  • Page 96 INDOOR UNIT PARTS NO. Q'TY PARTS NAME RAS-18YH4 HWRAS-25YH4 901 CABINET HWRAS-25YH4 902 VERTICAL AIR DEFLECTOR-L HWRAS-25YH4 903 VERTICAL AIR DEFLECTOR-R HWRAS-25YH4 904 FAN MOTOR 25W 1.1kg HWRAS-25YH4 905 ANTI VAIBRATION BUSHING HWRAS-25YH4 907 TANGENTIAL AIR FLOW FAN HWRAS-25YH4 908...
  • Page 97 OUTDOOR UNIT MODEL: RAC-18YH4 – 100 –...

  • Page 98: Outdoor Unit

    OUTDOOR UNIT PARTS No. Q'TY PARTS NAME RAC-18YH4 HWRAC-E08H BASE HWRAC-E08H COMPRESSOR 750W 8.1kg HWRAC-25YH4 COMPRESSOR RUBBER HWRAC-25YH4 PUSH NUT HWRAC-25YH4 CONDENSER HWRAC-E08H REVERSING VALVE (WITH COIL) HWRAC-E08H SERVICE VALVE ASSEMBLY HWRAC-E08H ELECTRIC EXPANSION VALVE HWRAC-E08H SOUND PROOF COVER ASSEMBLY HWRAC-E08H O.L.R COVER HWRAC-25YH4...
  • Page 99 RAS-18YH4 / RAC-18YH4 AW NO. 0004E Printed in Japan (TSK)

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