Bosch ACS 751 Setup guide

ACS 651/751
en Repair instructions
A/C service unit

1 689 975 223 2013-10-21| Robert Bosch GmbH
2 | ACS 751/651 |en
Contents English
1. Important information 4
2. Testing and resources 4
3. Description 5
3.1 ACS 651/751 5
3.1.1 Front view 5
3.1.2 Rear view 5
3.2 Components 6
3.2.1 Mounting place 6
3.2.2 Human Machine Interface (HMI) 6
3.2.3 Refrigerant cylinder 7
3.2.4 Pressure manifold 7
3.2.5 Vacuum pump 7
3.2.6 Compressor 7
3.2.7 Fan 7
3.2.9 I/O board 8
3.2.8 Human Machine Interface board
(main board) 8
4. Troubleshooting 9
4.1 By status messages 9
4.2 By symptoms 15
4.3 Entering the debug mode 16
4.4 Overview of actuators 16
5. Scales 16
5.1 Calibration of scales 16
5.1.1 Fresh Oil / used oil / UV dye scales 16
5.1.2 Calibration of the refrigerant tank
scale 17
5.2 Replacing scales 18
5.2.1 Replacing used oil/fresh oil/ UV dye
scale 18
5.2.2 Replacing scale assembly for
refrigerant cylinder 19
6. Panels 19
6.1 Opening the top panel 19
6.2 Opening the front panel 20
6.3 Opening the rear panel 20
6.4 Opening the right panel 20
6.5 Opening the left panel 20
6.6 Replacing the front wheels 21
6.7 Replacing the rear wheels 21
7. HMI module 21
7.1 Opening the HMI 21
7.2 Replacing the LCD 22
7.3 Replacing the printer 22
7.4 Replacing the keypad 23
7.5 Replacing the pressure gauges 23
8. Boards 24
8.1 Replacing the HMI board 24
8.2 Replacing the Switch Mode Power Supply
(SMPS) 24
8.3 Replacing the I/O board 24
9. Refrigerant cylinder 25
9.1 Replacing the refrigerant cylinder 25
9.2 Air purging 25
9.3 Replacing the air purge manifold on the
cylinder 26
9.4 Replacing the temperature sensor on the
cylinder 27
10. Pressure Manifold 28
10.1 Replacing the valve block of the pressure
manifold 28
10.2 Replacing the hoses between the
cylinder and the pressure manifold 28
10.3 Replacing the POE solenoid valve 29
10.4 Replacing the POE plug 30
11. Vacuum pump 30
11.1 Replacing the vacuum pump 30
11.2 Checking the vacuum pump function 31

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| ACS 751/651 | 3ACS 751/651 | 3| 3 en
12. Compressor and fan 31
12.1 Replacing the compressor 31
12.2 Checking the compressor function 32
12.3 Replacing the fan assembly 32
13. Replacing the wiring
harness 33
13.1 Replacing the wiring harness 1 33
13.2 Replacing the wiring harness 2 33
13.3 Replacing the wiring harness 3 33
13.4 Replacing the wiring harness 4 34
13.5 Replacing the wiring harness 5 34
13.6 Replacing the wiring harness 6 34
13.7 Replacing the connecting cable for the
temperature sensor 34
13.8 Replacing the USB host cable 34
13.9 Replacing the LED board cable 34
14. Replacing Hoses 35
14.1 Replacing the PA11 hose between the
compressor and the manifold 35
14.2 Replacing the PA11 hose for the HP/LP gauge 35
15. Replacing power supply 36
15.1 Replacing the cable socket 36
15.2 Replacing the fuse 36
14.3 Replacing the PA12 hose for the vacuum pump 36
14.4 Replacing the PA12 hose for the compressor 36
14.5 Replacing the silicon rubber hose for
Fresh-Oil, Used-Oil and UV-Dye 36
14.6 Replacing the hose between the oil separator
and the compressor 36
16. Test Points 37
17. Hydraulic circuit diagram 38
18. Electrical terminal diagram 39

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4 | ACS 751/651 | Important informationen
1. Important information
Installation and/or repairs may only be carried out by
trained and instructed Robert Bosch GmbH
customer service staff or organizations authorized by
Robert Bosch GmbH. Opening or modification of the
units by unauthorized persons will invalidate all
warranty entitlements.
Electrical systems and equipment may only be com-
missioned in proper condition (see Testing Technology
Information 0108_084 for details). This requirement
is met if, after modification or repair (initial test), it is
ensured that the requirements of the electrical engi-
neering regulations are adhered to. To verify this, tests
should be performed, the type and scope of which
should be based on the measures defined in the electri-
cal engineering regulations (e.g. in Germany BGV A3).
In Germany, the type and scope of the tests are de-
scribed in VDE 0701/0702 Part 1. The corresponding
national regulations must be adhered to.
2. Testing and resources
RGeneral tools for electricians and A/C mechanics
RDigital multimeter
RLoctite 577 for hoses
RCleaning medium (e.g. brake cleaner)
RCalibration weights for UV dye/oil bottles
(part number F 002 DG1 416)
RWeights for calibration of refrigerant scale - 6 kg
(part number F 002 DG1 650)

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Description | ACS 751/651 | 5ACS 751/651 | 5| 5 en
3. Description
3.1 ACS 751/651
3.1.1 Front view
0
2
4
68
10
0
5
10
15 20
25
30
35
12
HP
LP
14
!
2
ABC
3
DEF
6
MNO
ABC
123
8
TUV
7
PQRS
5
JKL
4
GHI
1
c
i
+
*
9
WXYZ
0
]
1 2 3
4
7
6
5
459897_18Nkv
8
9
10
Fig. 1: Front view
1 Handle
2 Human Machine Interface (HMI)
3 Top panel
4 Service hatch
5 HP quick coupler
6 Service hoses
7 LP quick coupler
8 Front wheel
9 Front service hatch
10 Inline filters
3.1.2 Rear view
459898_19Nkv
1
2
3
4
567
9
8
Fig. 2: Rear view
1 HMI support
2 Power switch
3 Left service hatch
4 Left panel
5 Rear panel
6. Rear wheel with brake
7 Power inlet
8 Power cable
9 Cable holder

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6 | ACS 751/651 | Descriptionen
3.2 Components
3.2.1 Mounting place
459898_21Nkv
12
3
4
5
6
7
9
8
10
11
12
13
14
15
Fig. 3: General overview
1 High pressure gauge
2 Low pressure gauge
3 Pressure manifold
4 Air purge manifold
5 Temperature sensor
6 Refrigerant cylinder
7 Oil separator
8 Compressor
9 Fan
10 Used oil bottle
11 Fresh oil bottle
12 Vacuum pump
13 UV dye bottle
14 Keypad
15 LCD
3.2.2 Human Machine Interface (HMI)
iC
!
HP
LP
1
2
3
5
4
6
7
1
2
3
4
5
6
7
8
9
*
+
0
ABC
123
]
459897_6Nkv
Fig. 4: ACS 751/651 HMI module
1 HP gauge
2 Status and warning light
3 LP gauge
4 LCD
5 Input keys
6 Selection and function keys
7 Printer

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Description | ACS 751/651 | 7ACS 751/651 | 7| 7 en
3.2.3 Refrigerant cylinder
459898_9Nkv
Fig. 5: Refrigerant cylinder overview
3.2.4 Pressure manifold
459898_13Nkv
Fig. 6: Pressure manifold overview
3.2.5 Vacuum pump
459898_7Nkv
Fig. 7: Vacuum pump overview
3.2.6 Compressor
459898_1Nkv
Fig. 8: Compressor overview
3.2.7 Fan
459898_14Nkv
Fig. 9: Fan overview

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8 | ACS 751/651 | Descriptionen
3.2.8 Human Machine Interface board (main board)
459898_29Nkv
1
2
3
456
8
9
10
11
7
Fig. 10: HMI Board (main board)
1 Connection to LCD
2 Coin battery CR2032
3 Connection to USB host (for firmware update)
4 Connection to LED
5 Connection to buzzer
6 Connection to keypad
7 Debug - Common port
8 I/O board communication port
9 Connection to printer data
10 Connection to printer power
11 Power from I/O Board
3.2.9 I/O board
459898_28Nkv
ACS-NP-IO-C-0030
12345
6
7
8
12 11 10
13
14
15
16
9
Fig. 11: I/O Board
1,2,3,4 Connections to scales
5 Connection to HMI board
6 Power to HMI
7 Power from SMPS
8,9Connection to solenoid valves
10 Connection to safety pressure switch
11 Connection to SMPS, Fan, Vacuum pump and compressor
12 Fuse
13 Connection to temperature sensor
14,15,16 Connection to pressure sensors

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Troubleshooting | ACS 751/651 | 9ACS 751/651 | 9| 9 en
4. Troubleshooting
4.1 By status messages
Error code Messages Actions
1001 RECOVERY
Service Timeout
RCheck for blockage in the vehicle A/C system.
RCheck for functionality of pressure sensor (PTA).
RCheck for compressor connections.
RCheck if internal parts of the manifold have blockage.
1002 RECOVERY
High pressure shutdown
RCheck for blockage in the vehicle A/C system.
RCheck for high pressure switch connection.
1003 RECOVERY
Used Oil bottle full
REmpty the used oil bottle.
RPerform scale reset.
RCheck for used oil bottle scale.
1004 RECOVERY
Refrigerant cylinder full
RWeight limit reached. Reduce quantity of refrig-
erant in internal refrigerant cylinder.
RScale is defective. Replace the scale.
RCheck for used oil bottle scale.
1005 RECOVERY
Used Oil Bottle Not Found
RCheck if the used oil bottle is disconnected. If the bot-
tle is disconnected, connect the bottle.
RCheck the used oil bottle scale.
2001 VACUUMING
High Pressure in vehi-
cle. Perform Recovery
The pressure is greater than 1400 mbar while vacuuming
RPress "Yes" to continue the recovery.
RPress "No" to abort the operation.
2002 VACUUMING
Leak detected
Leakage detected in the vehicle A/C system. Repair the vehicle A/C system.
3001 OIL RECHARGE
Service Timeout
RCheck the oil scale.
RCheck for blockage on the oil charge solenoid path.
3002 OIL RECHARGE
High pressure in vehi-
cle - Perform Recovery?
The pressure is greater than 1400 mbar while recharging.
RPress "Yes" to continue the recovery.
RPress "No" to abort the operation.
3003 OIL RECHARGE
High pressure in vehi-
cle - Perform Vacuuming?
The pressure is greater than 1400 mbar while recharging.
RPress "Yes" to continue the recovery.
RPress "No" to abort the operation.
3004 OIL RECHARGE
Insufficient Oil Quantity
ROil quantity is less than 30 ml. Refill the oil.
RReset the fresh oil bottle scale
RCheck the fresh oil bottle scale..
3006 OIL RECHARGE
Fresh oil Bottle Not Found
RCheck if the fresh oil bottle is disconnected. If the bot-
tle is disconnected, connect the bottle.
RCheck the oil bottle scale.
RCheck for blockage on the oil charge solenoid path.
4001 UV DYE RECHARGE
Service Timeout
RCheck for blockage in the hoses.
RCheck the oil scale.
RReplace the scale.
4002 UV DYE RECHARGE
High pressure in vehi-
cle - Perform Recovery?
The pressure is greater than 1400 mbar while recharging.
RPress "Yes" to continue the recovery.
RPress "No" to abort the operation.
4003 UV DYE RECHARGE
High pressure in vehi-
cle - Perform Vacuuming
The pressure is greater than 800 mbar while recharging.
RPress "Yes" to continue the vacuuming.
RPress "No" to abort the operation.
4004 UV DYE RECHARGE
Insufficient UV Dye quantity
RUV dye quantity is less than 30 ml. Fill the UV dye bottle.
RReset the UV dye bottle scale.
RCheck the UV dye scale.
RCheck for blockage on the oil charge solenoid path
4006 UV DYE RECHARGE
UV DYE Bottle Not Found
RCheck if the UV dye bottle is disconnected. If the bot-
tle is disconnected, connect the bottle.
RCheck for blockage on the oil charge solenoid path.
5001 R134aRECHARGE
Service Timeout
RCheck for blockage in the ACS 751/651.
RCheck if quick couplers are open.
RCheck for blockage in the hoses.
5002 R134a RECHARGE
Insufficient R134a quantity
Fill the internal refrigerant cylinder.
5003 R134a RECHARGE
Recharge Failed - Check Hoses
RCheck if HP and LP quick couplers are open.
RCheck if the HP and LP service hoses are blocked.
RCheck for blockage in the hoses

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10 | ACS 751/651 | Troubleshootingen
Error code Messages Actions
5004 R134a RECHARGE
High Pressure shutdown
RCheck the connection to high pressure switch
RCheck if the connection to the blue valve on the cylinder is open.
RCheck for blockage in the blue hose
5005 R134a RECHARGE
Refrigerant Cylinder Full
RWeight limit reached.
RReduce quantity of refrigerant in internal refrigerant cylinder.
RScale is defective. Replace the scale.
5006 R134a RECHARGE
High Pressure in Vehi-
cle - Perform Recovery?
RPress "Yes" to perform recharge.
RPress "No" to abort the operation.
5007 R134a RECHARGE
High pressure in vehi-
cle - Perform Vacuuming
RPress "Yes" to perform vacuuming.
RPress "No" to abort the operation.
7100 Safety Switch
High pressure shutdown
RAllow the unit to cool for 30 minutes and switch on the unit. Try re-
covery/hose drain. Check if the blue knob on the internal refrig-
erant tank is closed. Open the blue knob If it is closed.
RCheck if the electrical connections to the pressure switch are disconnected.
RCheck if there is blockage in the discharge tube/manifold/blue hose be-
tween the tank and valve block. Rectify if there is leakage.
RIn debug mode switch on CX and check if compressor is functioning.
7102 PSA
Sensor Connection Failed
RTemporarily interchange the PSA and PSV cable connection at the sen-
sor side. If the error is still with PSA sensor, then replace the top block.
RCheck the electrical continuity of the sensor cable including connector at both
ends for each individual wires. If continuity test fails, then change the cable.
RChange the I/O board.
7202 PST
Sensor Connection Failed
RTemporarily interchange the PST and PSV cable connection at the sen-
sor side. If the error is still with PST sensor, then replace the top block.
RCheck the electrical continuity of the sensor cable including connector at both
ends for each individual wires. If continuity test fails, then change the cable.
RChange the I/O board.
7302 PSV
Sensor Connection Failed
RTemporarily interchange the PSV and PSA cable connection at the sen-
sor side. If the error is still with PSV sensor, then replace the top block.
RCheck the electrical continuity of the sensor cable including connector at both
ends for each individual wires. If continuity test fails, then change the cable.
RChange the I/O board.
7402 Tank Temperature
Sensor Connection Failed
RCheck the electrical continuity of the sensor ca-
ble including connector at both ends.
RMeasure the resistance across two terminals of the temper-
ature sensor. If the measured resistance is found to be in-
finity or zero, change the temperature sensor.
RReplace the I/O board.
7403 Tank Temperature
Sensor Connection Failed
RCheck the electrical continuity of the sensor ca-
ble including connector at both ends.
RMeasure the resistance across two terminals of the temper-
ature sensor. If the measured resistance is found to be in-
finity or zero, change the temperature sensor.
RReplace the I/O board.
7501 R134a
Timeout
Replace the I/O board.
7502 R134a
Sensor Connection Failed
RMeasure the resistance across:
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7503 R134a
Sensor Connection Failed
RMeasure the resistance across
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7601 UV Dye
Timeout
Replace the I/O board.

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Error code Messages Actions
7602 UV Dye
Sensor Connection Failed
RMeasure the resistance across
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7603 UV Dye
Sensor Connection Failed
RMeasure the resistance across:
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7701 Fresh Oil
Timeout
Replace the I/O board.
7702 Fresh Oil
Sensor Connection Failed
RMeasure the resistance across:
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7703 Fresh Oil
Sensor Connection Failed
RMeasure the resistance across
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7801 Used Oil
Timeout
Replace the I/O board.
7802 Used Oil
Sensor Connection Failed
RMeasure the resistance across:
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7803 Used Oil
Sensor Connection Failed
RMeasure the resistance across:
- Red-Black
- Green-White
If any of the two measurement shows inifinite resistance, change the load sensor.
RChange the I/O board.
7804 Used Oil
Invalid Range
RAllow the unit to cool for 30 minutes and switch on the unit. Try re-
covery/hose drain. Check if the blue knob on the internal refrig-
erant tank is closed. Open the blue knob If it is closed.
RCheck if the electrical connections to the pressure switch are disconnected.
RCheck if there is blockage in the discharge tube/manifold/blue hose be-
tween the tank and valve block. Rectify if there is leakage.
RIn debug mode switch on CX and check if compressor is functioning.
8000 SYSTEM ERROR
Retry Operation. Contact tech-
support if problem persists
Check the cable connection between the HMI board and the I/O board.
or
Replace the HMI board.
9001 FIRMWARE UPDATE Retry Op-
eration. Contact tech-sup-
port if problem persists.
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9201 SYSTEM ERROR
No USB detected
Check if the USB disk is connected to the USB port.
9203 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists.
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9204 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists.
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9205 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9206 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9207 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9208 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.

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12 | ACS 751/651 | Troubleshootingen
Error code Messages Actions
9209 SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
920A SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
920B SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
920C SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
920D SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
920E SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
920F SYSTEM ERROR Retry Op-
eration. Contact tech-sup-
port if problem persists
RCheck the HMI board.
RCheck the USB connection.
RReplace the HMI board.
9300 SELF TEST FAILED
View Detail?
Press "Yes" to view details. Press "No" to continue.
9400 RTC Failed Replace the HMI board.
9600 PRINTER
Out of paper
RCheck if paper roll is present in the printer. If not, insert paper roll.
To order printer paper, use the order number F 002 DG1 450.
A101 INTERNAL BOTTLE FILL
Service Timeout
RCheck for blockage in ACS 751/651.
RCheck R134a scale.
A102 INTERNAL BOTTLE FILL
Used Oil bottle full
Check if the used oil bottle is full. If the bottle is full, empty the bottle.
A103 INTERNAL BOTTLE FILL Re-
frigerant Cylinder Full
RWeight limit reached. Reduce quantity of refriger-
ant in the internal refrigerant cylinder.
RRefrigerant cylinder scale is defective. Replace the scale.
A104 INTERNAL BOTTLE FILL
High Pressure shutdown
RCheck for blockage in the vehicle A/C system.
RCheck the connection to the high pressure switch.
RCheck if the connection to the blue valve on the cylinder is open.
RCheck for blockage in the blue hose.
A105 INTERNAL BOTTLE FILL
Low Pressure - Check ex-
ternal cylinder valve
RCheck if the valve on the external cylinder is open.
RCheck if R134a is available in the external cylinder.
A202 SHORT FLUSHING
Service timeout
RCheck for blockage in the ACS 651/751.
A203 SHORT FLUSHING
Insufficient R134a quantity
Fill the internal refrigerant cylinder.
A204 SHORT FLUSHING
Leak Detected
Repair the vehicle A/C system or part under flushing.
A205 SHORT FLUSHING
High Pressure shutdown
RCheck for blockage in the vehicle A/C system.
RCheck the connection to the high pressure switch.
RCheck if the connection to the blue valve on the cylinder is open.
RCheck for blockage in the blue hose.
A206 SHORT FLUSHING
High Pressure in vehi-
cle. Perform Recovery?
The pressure is greater than 1400 mbar while vacuuming Press "Yes"
to continue the recovery. Press "No" to abort the operation.

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Troubleshooting | ACS 751/651 | 13ACS 751/651 | 13| 13 en
Error code Messages Actions
A207 EXTENDED FLUSHING
Used Oil bottle Full
Reduce quantity of used oil in the used oil bottle. Perform scale reset.
A208 SHORT FLUSHING
Refrigerant Cylinder Full
RWeight limit reached. Reduce quantity of refrig-
erant in internal refrigerant cylinder.
RRefrigerant cylinder scale is defective. Replace the scale.
A209 SHORT FLUSHING
Recharge Failed. Check Hoses
Perform action as indicated
A302 EXTENDED FLUSH-
ING Service Timeout
Check for blockage in ACS 751/651.
A303 EXTENDED FLUSHING
Insufficient R134a quantity
Fill R134a to the internal cylinder.
A304 EXTENDED FLUSHING
Leak Detected
Check for leakage in the part under flushing.
A305 EXTENDED FLUSHING
High pressure shutdown
Check for blockage in the ACS 651/751.
A306 EXTENDED FLUSHING
High pressure in vehi-
cle - Perform Recovery?
The pressure is greater than 1400 mbar while vacuum-
ing. Perform recovery and restart flushing.
A307 EXTENDED FLUSHING
Used Oil bottle full
REmpty the used oil bottle.
RPerform scale reset
RCheck the used oil bottle scale.
A308 EXTENDED FLUSHING
Refrigerant cylinder full
RWeight limit reached. Reduce quantity of refrig-
erant in internal refrigerant cylinder.
RRefrigerant tank scale is defective. Replace the scale.
A309 EXTENDED FLUSHING
Recharge Failed. Check Hoses
Perform action as indicated.
A401 CALIBRATION
No weight detected
RPerform scale reset of the oil bottle load sensors.
RCalibrate all the load sensors.
RCheck the electrical connection between all the load sensors and I/O board.
A601 REFRIGERANT TOP UP
Service Timeout
RCheck if the vehicle A/C system is on.
RCheck for blockage in the ACS 751/651.
RCheck the refrigerant cylinder scale.
RCheck for blockage in the hoses
A602 REFRIGERANT TOP UP
Insufficient R134a Quantity
Fill the internal refrigerant cylinder.
A701 CALIBRATION CHECK
Weight Not Placed
RPlace a valid weight.
RCheck for refrigerant scale.
A702 CALIBRATION CHECK
Failed
RPerform calibration again.
A901 AIR PURGE
Service Timeout
RCheck the temperature sensor.
RCheck the solenoid valve on the air purge manifold.
A20A SHORT FLUSHING
Used Oil Bottle Not Found
RCheck if the used oil bottle is disconnected. If the bot-
tle is disconnected, connect the bottle.
RCheck the used oil bottle scale.
A30A EXTENDED FLUSHING
Used Oil Bottle Not Found
RCheck if the used oil bottle is disconnected. If the bot-
tle is disconnected, connect the bottle.
RCheck the used oil bottle scale
C001 OIL RECHARGE
Service Timeout
RCheck the oil scale.
RCheck for blockage on the oil charge solenoid path.
C002 OIL RECHARGE
High pressure in vehi-
cle. Perform Recovery
The pressure is greater than 1400 mbar while recharging.
Perform recovery

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14 | ACS 751/651 | Troubleshootingen
Error code Messages Actions
C003 OIL RECHARGE
High pressure in vehi-
cle. Perform Vacuuming
The pressure is greater than 900 mbar while recharging.
Perform vacuuming
C004 OIL RECHARGE
Insufficient Oil Quantity
ROil quantity is less than 30 ml. Refill the oil.
RReset the fresh oil bottle scale
C006 OIL RECHARGE
Fresh oil Bottle Not Found
RCheck if the fresh oil bottle is disconnected. If the bot-
tle is disconnected, connect the bottle.
D001 A/C PERFORMANCE TEST
Refrigerant cylinder full
RWeight limit reached. Reduce quantity of refrig-
erant in internal refrigerant cylinder.
RLoad cell is defective. Replace the load cell.
D002 A/C PERFORMANCE TEST
Service Timeout
RCheck for leakage / blockage in the HP/ LP hoses of the ACS 751/651.
RCheck if the quick couplers are connected properly to the ser-
vice connections on the vehicle A/C system.
D003 A/C PERFORMANCE TEST
High pressure in the sys-
tem, Perform Hose drain
The pressure is greater than 1400 mbar. Perform hose drain.
D004 A/C PERFORMANCE TEST
Insufficient R134a Quantity
Fill the internal refrigerant cylinder.
D005 A/C PERFORMANCE TEST
High pressure shutdown
RCheck the connection to the high pressure switch
RCheck if the hose connection to the blue valve on the cylinder is open.
RCheck for blockage in the blue hose.
) The message "Service Timeout" indicates the service timeout for any service phase which is in progress. The following table indicates the
service timeout duration for different service phases.
Service phase Timeout duration (mins)
Recovery (refrigerant recovery) 90
Recharge oil 3
Recharge UV dye 3
Recharge refrigerant 15
Hose drain 5

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Troubleshooting | ACS 751/651 | 15ACS 751/651 | 15| 15 en
4.2 By symptoms
Symptom Description Troubleshooting
The gauge pressure
rises after the recov-
ery and recycling phase
Previous recovery was incomplete
/leak across the valves
RRepeat recovery and check the gauge pres-
sure again at the end of recovery.
RCheck if the plunger has worn out or if
there is contamination in the valve block.
Caution: Close the red and blue
valves on the internal refrigerant
cylinder before opening the solenoid.
The vacuum
phase does not start.
The vacuum pump does not start. RIf the gauge pressure is high, per-
form recovery before vacuuming.
RCheck the electrical and pipe connection to
the vacuum pump and associated solenoid.
RIf the vacuum pump is on and yet, the
pressure does not decrease, check for
the pipe connection/blockage.
The leakage test at the end
of the vacuum phase failed.
Duration of the vacuum phase is too short. Vacuum phase duration is approximately 30 minutes
for vehicles with larger A/C systems (for example,
trucks require longer vacuum time).
Leakage in vehicle A/C system. Repair the vehicle A/C system.
Leakage in the ACS 751/651. Check HP, LP hoses and their connections.
Check if the plunger has worn out or if
there is contamination in the valve block.
Recharge is very slow or is
interrupted before the re-
quired quantity has been
filled to the vehicle.
Insufficient refrigerant in the
internal refrigerant container.
Fill internal refrigerant cylinder with fresh re-
frigerant. The optimum quantity is 8 kg - 9 kg.
Pressure in the R134a cylinder is too low. Fill internal refrigerant cylinder
with fresh refrigerant. The optimum pres-
sure is approximately 6-7 bar .
The quantity of refrig-
erant filled does not
match the set amount
Scale for the refrigerant cylin-
der is not calibrated.
Check the scale for the refrigerant cylinder with
a known weight. If the value does not match, cali-
brate the scale. See chapter 5 for more information.
Mechanical obstruction for the scale
of the refrigerant cylinder.
RCheck if the movement of the scale and the re-
frigerant cylinder is blocked mechanically by oth-
er components.
RRemove any obstructions for the scale.
Compressor does not start RPower supply interrupted
RCheck pressure switch
Check the electrical connection of the power switch,
pressure switch, compressor and capacitor of the
compressor.
White smoke emanates
from the vacuum pump.
Aspirated ambient air Inspect the vehicle A/C system and also the
ACS 751/651 for leaks and repair. Small quan-
tities of smoke in the first few minutes of op-
eration of the vacuum phase are permitted.

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16 | ACS 751/651 | Scalesen
4.3 Entering the debug mode
1. Connect the power cable to the mains supply.
2. Switch on the power supply.
3. Press the Ckey and power on the ACS 751/651.
4. Enter the password 33284.
"The "Debug Mode" menu is displayed.
4.4 Overview of actuators
iSee chapter 15 for the hydraulic circuit diagram.
Actuator name Description
CTRL Entry to internal tank
CX Compressor
CXOL Compressor oil return
FA Fan
HL Connection from LP to HP
HPS High pressure switch
IN Entry to liquefier
LP Entry through LP hose
OD Oil drain
OI Oil recharge
PRIN Passage for clearing
PTA/PSA Pressure sensor for accumulator
PTT/PST Pressure sensor for tank
PTV/PSV Pressure sensor for vacuuming
PU Air purge on refrigerant cylinder
RE Connection between internal refrig-
erant cylinder and manifold
UV UV dye recharge
VC Vacuum pump
VISO Connection between vacu-
um pump and manifold
5. Scales
5.1 Calibration of scales
5.1.1 Fresh Oil / used oil / UV dye scales
1. Open the service hatch on the front panel.
2. In the main menu, select "ACS Settings" and press E.
?The ACS Settings menu is displayed.
3. Select "Calibration".
4. Select "Balance Calibration".
5. Enter the password 227.
?The following screen is displayed.
6. Select any of the sensors - fresh oil, used oil or UV dye.
?The following screen is displayed.
7. Detach the bottle from the connector.
8. Select "Remove Bottle".
9. Attach the calibrating weight to connector of the oil
/ UV dye sensors.

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Scales | ACS 751/651 | 17ACS 751/651 | 17| 17 en
iThe calibrating weight has couplings on either ends
(Fig.12). Depending on the sensor that is calibrated,
the calibrating weight can be connected to any of
the sensors.
1 2
459897_38Nkv
Fig. 12: Calibrating weight
Fig. 13: Attaching the standard calibrating weight for the fresh
oil / UV dye scales
10. Select "Place Standard Weight".
11. Enter the value of the calibrating weight.
12. Select "Input Placed Weight"
13. Select "Start calibration".
iAfter the calibration is complete, the message
Calibration Complete is displayed.
14. Detach the calibrating weight from the scale.
15. Repeat the procedure for all the three scales.
16. Attach the oil and UV dye bottles to the connectors.
17. Close the service hatch.
"You have successfully calibrated the scales for fresh
oil / used oil / UV dye bottles.
5.1.2 Calibration of the refrigerant tank scale
1. Apply the brakes.
2. Open the rear panel.
3. Connect the power cable to the power socket.
4. Perform hose drain.
5. Close the red and blue taps on the cylinder.
6. Disconnect the hoses between the tank and the mani-
fold.
7. In the main menu, select "ACS Settings" and press E.
?The ACS Settings menu is displayed.
8. Select "Calibration".
9. Select "Balance Calibration".
10. Enter the password 227.
?The following screen is displayed.
11. Select "R134a" and press E.
?The following screen is displayed.
12. Select "Start Calibration".
13. Attach the standard calibration weight (Fig. 14) to
the neck of the refrigerant cylinder without jerking
the tank.

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18 | ACS 751/651 | Scalesen
459898_43Nkv
Fig. 14: Attaching the calibrating weight to the
refrigerant cylinder
14. Select "Place Standard Calibration Weight".
15. Enter the value of the calibrating weight.
iThe actual value is embossed on the calibrating
weight.
16. Select "Input Standard Weight".
17. Select "Calibrate". If you wish to abort the calibra-
tion, press c.
?The calibration process starts. Once the calibra-
tion is complete, the message Calibration
complete is displayed.
"You have successfully calibrated the scale for the
refrigerant tank.
5.2 Replacing scales
5.2.1 Replacing used oil/fresh oil/ UV dye scale
4589898_23Nkv
Fig. 15: Scales assembly
1. Switch off the ACS 751/651.
2. Disconnect the mains connection.
3. Open the front service hatch and disconnect the oil
and UV dye bottles.
4. Open the front panel and top panel (Chap. 6.1,6.2).
5. Disconnect the connections from the scale to the I/O
board. .
6. Undo the screws on the top and bottom of the re-
taining plate for the scale.
7. Place the new scale into position.
8. Tighten the screws on the retaining plate.
9. Restore the I/O connections to the scale.
10. Close the front panel.
11. Connect the power cable to the mains supply.
12. Switch on the mains supply.
13. Turn on the power switch.
14. In the main menu, select "ACS Settings".
15. Perform calibration with the standard weight.

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5.2.2 Replacing scale assembly for refrigerant
cylinder
Warning - Danger of frostbite!
During repair work on the ACS 751/651
refrigerant in liquid or gaseous form can
escape and cause frostbite to the body.
¶Close valves on refrigerant cylinder.
¶Wear protective goggles.
¶Wear protective gloves.
1. Remove the refrigerant tank from the mounting posi-
tion (Chap. 8.1).
2. Place the cylinder outside the ACS 751/651 unit.
!Ensure the hydraulic connections are not strained or
damaged.
3. Disconnect the electrical connections from the scale
to the I/O board.
4. Remove the earthing connection to the scale assembly.
5. Unfasten the scale assembly from the chassis.
6. Complete the earthing connection to the new scale
assembly.
7. Fix the new scale assembly to the chassis.
8. Make the connections from the scale assembly to the
to the I/O board.
9. Mount the cylinder on the scale assembly.
10. Close the rear panel.
459898_8Nkv
Fig. 16: Refrigerant cylinder scale assembly
iEnsure that the cylinder is filled with the refrigerant
before service is performed.
6. Panels
6.1 Opening the top panel
1. Apply the brakes.
2. Switch off the ACS 751/651.
3. Lower the HMI module.
4. Unfasten the screws on the top and on either sides
of the panel.
5. Lift the top panel up.
4589898_20Nkv
1
Fig. 17: Opening the top panel
1 Top panel

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20 | ACS 751/651 | Panelsen
6.2 Opening the front panel
1. Apply the brakes.
2. Switch off the ACS 751/651.
3. Remove the top panel
4. Open the front service hatch.
5. Detach the bottles from the connectors.
6. Disconnect the service hoses.
7. Unfasten the screws on either sides of the front
panel.
8. Pull out the front panel.
459898_31Nkv
1
Fig. 18: Opening the front panel
1 Front panel
6.3 Opening the rear panel
1. Apply the brakes.
2. Switch the ACS 751/651 off.
3. Remove the mains connection.
4. Unfasten the screws on either sides of the rear panel.
5. Pull out the rear panel.
459898_30Nkv
2 1
Fig. 19: Opening the rear panel
1 Rear panel
6.4 Opening the right panel
1. Apply the brakes.
2. Switch the ACS 751/651 off.
3. Unfasten the knob screws on the service hatch and
remove the service hatch.
4. Unfasten the screws on the right panel.
5. Pull out the right panel.
459898_11Nkv
1
Fig. 20: Opening the right panel
1 Right panel
6.5 Opening the left panel
1. Apply the brakes.
2. Switch the ACS 751/651 off.
3. Disconnect the mains connection.
4. Unfasten the knob screws on the service hatch and
remove the service hatch.
5. Unfasten the screws on the left panel.
6. Pull out the left panel.
459898_10Nkv
1
Fig. 21: Opening the left panel
1 Left panel