ABS ASTON MARTIN DB7 1997 User Guide

Air Conditioning
Working Practices O" 15-^?
Working Practices
General
Be aware of, and comply
with,
all health and safety
requirements.
Before beginning any repair or service procedure,
disconnect the vehicle battery ground connection
and protect the vehicle from dirt or damage.
Work in a well ventilated, clean and tidy area.
Recovery and chargeequipment must comply
with,

or exceed the standard detailed in the General
Description.
Handling Refrigerant
Wear eye protection at all times.
Use gloves, keep skin that may come into contact
with refrigerant covered. If the refrigerant comes
into contactwith youreyesorskin wash the affected
area immediatelyw'ith cool water and seek medical
advice, do not attempt to treat yourself.
Avoid inhaling refrigerant vapour, it wil
your respiratory system.
irritate
Never use high pressure compressed air to flush out
a system. Under certain circumstances a
combination of HFC 134A and compressed air in
the presenceofa source ofcombustion (for instance,
welding or brazing equipment), results in an
explosion that releases toxic compounds into the
atmosphere.
The refrigerant and CFC 12 must never come into
contact with each other
as
they form an inseparable
mixture that can only be disposed of by incineration.
Do not vent refrigerant directly into the atmosphere,
always use approved recovery equipment.
Refrigerant is costly but it can be recycled. Clean
the refrigerant, using the recovery equipment and
reuse it.
Carry out LeakTestsonly with an electronic analyser
dedicated to Refrigerant El 34A.
Do not attemptto guess the amount of refrigerant in
a system, always recover it and recharge with the
correct charge weight. Do not depress the charge or
discharge port valves to check for the presence of
refrigerant.
Handling Lubricating Oil
Avoid breathinglubricantmist,itwillcauseirritation
to your respiratory system.
Always decant fresh oil from a sealed container. Do
not leave oil exposed to the atmosphere for any
reason other than to fill or empty a system; PAG oil
is hygroscopic (it absorbs water) and iscontaminated
rapidly by atmospheric moisture.
Following the recovery cycle do not reuse the oil
when it has been separated from the refrigerant;
dispose of the oil safely.
System Maintenance
Do not leave the system open to the atmosphere. If
a unit or part of the system is left open for more than
five minutes, it is advisable to renew the receiver-
dryer. There is not a safe period in which work is to
be carried out. Always plug pipes and units
immediately after disconnection and only remove
plugs when re-connecting.
If replacement parts are supplied without transit
plugs and seals do not use the parts. Return them to
your supplier.
Diagnostic equipment for pressure, mass and
volumeshouidbecalibrated regularly and certified
by a third party organisation.
Use extreme care when handling and securing
aluminium fittings, always use a backing spanner
and take special care when handlingtheevaporator.
Use only the correct or recommended tools for the
job and apply the manufacturer's torque
specifications.
Keep the working area, all components and tools

clean.

8-8 May 1996

Air Conditioning //~-->> ^/zz:^^ • ^ ^
General Svstem Procedures ' —"^ ^ '^ General System Procedures
From the condenser the liquid passes into the Receiver-Drier which has three functions:
• Storage vessel for varying system refrigerant demands.
• Filter to remove system contaminants.
• Moisture removal via the desiccant.
With the passage through the receiver-drier completed the, still high pressure liquid refrigerant, enters the Expansion
Valve where it is metered through a controlled orifice which has the effect of reducing the pressure and temperature.
The refrigerant, now in a cold atomised state, flows into the Evaporator and cools the air which is passing through
the matrix.
As heat is absorbed by the refrigerant it once again changes state, into a vapour, and returns to the compressor for
the cycle to be repeated (Fig. 5).
There is an automatic safety valve incorporated in the compressor which operates should the system pressure be
in excess of
41
bar. The valve re-seats when the pressure drops below 35 bar.
Note: The division of HIGH and LOW side is simply the
system pressure
differential created by the
compressor
discharge

(pressure),
suction
(inlet)
ports and
the
relative inlet and outlet
ports
of the
expansion
valve.
This
differential is critical to
system

fault
diagnosis
and efficiency checks.
System Protection
The trinary pressure switch, located in the liquid line, cuts electrical power to the compressor clutch if the system
pressure is outside of the range of 2 Bar
(1
st Function) to 27 Bar (2nd Function). The third function is to switch on
the cooling fans when pressure exceeds 20 bar.
General System Procedures
Leak Test
Faults associated with low refrigerant charge weight and low pressure may be caused by leakage. Leaks traced to
mechanical connections may be caused by torque relaxation or joint face contamination. Evidence of oil around
such areas is an indicator of leakage. When checking for non visible leaks use only a dedicated Refrigerant El 34A
electronic analyser and apply the probe all round the joint connection. Should a leak be traced to a joint, check that
the fixing is secured to the correct tightening torque before any other action is taken.
Do not forget to check the compressor shaft seal and evaporator.
Note: Never
use
a dedicated
CFC 12
or
naiced
flame type
analyser.

Charge Recovery (System Depressurisation)
The process of refrigerant recovery depends on the basic characteristics of your chosen recovery-recycle-recharge
equipment, therefore, follow the manufacturers instructions carefully. Remember that compressor oil may be drawn
out of the system by this process, take note of the quantity recovered so that it may be replaced.
CAUTION: Observe all relevant safety requirements.
• Do not vent refrigerant directly to atmosphere and always use approved recovery-recycle-recharge
equipment.
• Wear suitable eye and skin protection.
• Do not mix the refrigerant with CFC 12.
• Take note of the amount of recovered refrigerant, it indica
tes the
state of the
system
and
thus the
magnitude
of any problem.
8-12 May 1996

^2?
Air Conditioning
General System Procedures
Evacuating the System
This process, the removal of unwanted air and moisture, is critical to the correct operation of the air conditioning

system.
The procedures depends on the characteristics of the recovery-recycle-recharge equipment and must be
carried out exactly in accordance with the manufacturers instructions.
Moisture can be highly destructive and may cause internal blockages due to freezing, but more importantly, water
suspended in the PAG oil will damage the compressor. Once the system has been opened for repairs, or the
refrigerant charge recovered, all traces oi moisture must be removed before recharging with new or recycled
refrigerant.
Adding Compressor Lubricating Oil
Oil can be added by three methods, two of which are direct into the system
• via the recovery-recycle-recharge station
• by proprietary oil injector.
Equipment manufacturer's instructions must be adhered to when using direct oil introduction.
The third method may be required because of rectification work to the existing compressor, or the need to fit a new
compressor. From an existing compressor, drain the oil into a measuring cylinder and record the amount. Flush the
unit out with fresh PAG oil and drain thoroughly. Refill the compressor with the same amount of PAG oil that was
drained out originally and plug all orifices immediately ready for refitting to the vehicle. The transit lubricating oil
must be drained and discarded from a new compressor before it may be fitted. An adjustment should be made to
the system oil level by taking into account:
• the quantity found in the original compressor
• the quantity deposited in the recovery equipment oil separator from the charge recovery operation.
Typically, 80 ml can be drained from the original compressor and 30 ml found in the oil separator; the sum of these
volumes (80 + 30 = 110 ml) is the amount of fresh PAG oil that must be put into the new compressor prior to fitting.
Hote:
The
discrepancy
between
this
figure
and
the
nominal capacity of
135
ml is
caused
by normally not
recoverable
oil being
trapped in
components
such
as
the receiver-drier or
evaporator.

The above statements are only true if there is no evidence of a leak. Where a leak has been detected and rectified,
the compressor must be refilled with the specified quantity.
Caution: Always decant
fresh
oil from a sealed container and do not leave oil exposed to the
atmosphere.
PAG oil is very
hygroscopic
(absorbs
water) and rapidly
attracts
atmospheric moisture.
PAG oil must
NEVER
be mixed with mineral
based
oils.
Do not
reuse
oil following a recovery cycle,
dispose
of it
safely.

Depending on the state of the air conditioning system immediately prior to charge recovery and the rate of recovery,
an amount of oil is drawn out with the refrigerant. The quantity is approximately 30 to 40 mi; this may vary, and
the figure is given only for guidance. It is most important that the oil separator vessel in the recovery equipment is
clean and empty at the start of the process so that the amount drawn out may be accurately measured.
May 1996 8-13

Air Conditioning
Refrigeration /s:s^°27
Refrigeration
Safety Precautions
The air conditioning system is designed to use only
Refrigerant E134A (dichlorodifluoromethane). Extreme
care must betaken NOT to use
a
methylchloride refrigerant.
The chemical reaction between methylchloride and the
aluminium parts ofthe compressor results in the formation
ofproductswhich burn spontaneously on exposure toair,
or decompose with violence in the presence of moisture.
The suitable refrigerant is supplied under the following
names.
El 34A KLEA or equivalent
Warning: Take care when handling refrigerant. Serious
damage will occur if it is allowed to come into
contact with the eyes. Always wear with goggles
and gloves when working with refrigerant
First Aid
If refrigerant should come into contact with the
eyes or
skin,
splash the eyes or affected area with
cold water for several minutes. DO NOT RUB. As
soon as possible thereafter, obtain treatment from a
Doctor or an eye specialist.
Good Practice

1.
Protective sealing plugs must be fitted to all
disconnected pipes and units.

2.
Theprotectivesealingpiugsmustremain inposition
on ail replacement components and pipes until
immediately before assembly.
3. Any part arriving for assembly without sealing
plugs in position must be returned to the supplier as
defective.

4.
It is essential that a second backing spanner is
always used when tightening or loosening all joints.
This minimises distortion or strain on components
or connecting hoses.
5. Components must not be lifted by connecting

pipes,
hoses or capillary tubes.
6. Care must be taken not to damage fins on the
condenser or evaporator matrices. Any damage
must be rectified by the use of fin combs.
7. Before assembly oftube and hosejoints, use
a
small
amount of clean new refrigerant oil on the sealing
seat.
8. Refrigerant oil for any purpose must be kept very
clean and capped at all times. This prevents the oil
absorbing moisture.
9. Before assembly the condition of joints and flares
must be examined. Dirt and even minor damage
will cause leaks at the high pressure points
encountered in the system.

10.
Dirty end fitting can only be cleaned using a cloth
wetted with alcohol.

11.
Afterremovingsealingplugsand immediatelybefore
assembly, visually check the bore of pipes and
components. Where any dirt or moisture is

discovered,
the part must be rejected.
12. Ail components must be allowed to reach room
temperature before sealing plugs are removed.
This prevents condensation should the component
be cold initially.

13.
Before finally tightening hose connections ensure
that the hose lies in the correct position, is not
kinked or twisted and will not be trapped by
subsequent operations, e.g., refitting or closing
bonnet.

14.
Check that hoses are correctly fitted in clips or
straps.

15.
The compressor must be stored horizontally with
the sump down. It must not be rotated before fitting
and charging. Do not remove the shipping plate
until immediately before assembly. Always use
new "O" ring seals in those joints that incorporate

them.
"O" ring seals should be coated with
compressor oil before fitting.

16.
Components or hoses removed must be sealed
immediately after removal.
1 7. Afterthe system has been opened the receiver-drier
must be renewed.

18.
Before
testing,
run the engine until normal running
temperature is reached. This ensures that sufficient
vacuum is available for test. For cooling tests the
engine must be running for the compressor clutch
to operate.
8-34 May 1996

Air Conditioning
Compressors ^?
Evaporator
Figure 3.
Receiver-Drier
The receiver drier (Fig. 1) accepts high pressure
warm refrigerant liquid from the condenser and
del ivers it via an expansion valve to the evaporator.
It contains a quantity of molecular sieve desiccant
to remove moisture from the refrigerant, and
a
fi Iter
to removecontaminants.lt also
a
providesa reservoir
of refrigerant for the evaporator under varying
operating conditions.
The evaporator consists of a refrigerant coil mounted
in a series of thin fins to provide a maximum
amount of heat transfer in a minimum amount of

space.
It is housed in the air conditioning unit and
all air entering the system passes across its
coil.

The evaporator receives refrigerant from the
thermostatic expansion valve as a low pressure
cold atomised liquid. As this cold liquid passes
through the evaporator coils, it absorbs heat from
the surrounding air and changes into
a
low pressure
warm vapour.
Expansion Valve
The expansion valve is the dividing point between
the high and low pressure sides of the system. It
automatically meters high pressure, warm liquid
refrigerant via a metering orifice into the low
pressure, cold side of the evaporator matrix. The
valve senses outlet pipe temperature, inlet pipe
pressure and regulates the flow of refrigerant into
the evaporator to ensure that only vaporised
refrigerant appears at the outlet.
Figure 1.
8-36 May 1996

^=2?
The Aston Martin Lagonda Diagnostic System
Users Guide
Software
Software for the PDU system is supplied on CD ROM
discs and supports diagnosis on the following control

units:

Zytek Engine Management System (95 MY)
EEC-V Engine Management System (97 MY)
CM 4L80-E Transmission Controller
PATS - Passive Anti Theft System
Teves Mk II ABS System (95 MY)
Teves Mk IV ABS System (97 MY)
Valeo Air Conditioning System
PMC Airbag System
Megamoss Security System
Autoliv Drivers Seat Belt Pretensioner
(where fitted)
All of these systems are supported in English, French,

Italian,
German and Japanese.
In addition to the specific system software listed above,
thePDU isalsoequipped with general purpose software
to provides multimeter, printing and PDU training
options.
Software for 95 and 97 Model Year Vehicles
Software for both the 95 and 97 model year vehicles is

provided.

The PDU system requires a Vehicle Interface Adaptor
(VIA) to communicate with the control units of 95
model year vehicles.
Communication with 97 model year control units is
principally via an Aston Martin multi-protocol adaptor
to 2 inbuilt diagnostic sockets in the vehicle. Only the
air conditioning unit requires the VIA on 97 model year
vehicles.
If the multimeter function is used, the Vehicle Battery
Adaptor (VBA) will be required to provide the basic
supply and ground levels for the multimeter.
Software Loading and Selection
Ensure that the system is powered up and that the PDU is
correctly connected to the base station. Check and if
necessary load the DB7 software CD Revision 002. (see
the installation guide)
Switch 'on' the PDU which will run through two front
screens and then load the following initial PDU software.
Operating System
Main Menu
Selector
Digital Multimeter
Interactive Training
September 1996 9-29

^?
The Aston Martin Lagonda Diagnostic System
Users Guide
Climate Control Diagnostics
The air conditioning control module is located at the right
end of the air conditioning unit. Since this controller uses
a unique communications protocol, the PDU must be
connected directly to the unit via the Vehicle Inerface
Adaptor as shown in the following cable setup screen.
Cable Setup
Adigitalmicroprocessorwithin the control module receives
data signals from the operator controlled switches.
Comparison of these signals with those returned from
system temperature sensors and feedback devices results
in the appropriate output voltage changes needed to vary:
Blower motor speed, flap position and the solenoids
which respond to operator selected temperature demand.
The air from two blower motors is passed through the
evaporator matrix which, depending on the positions of
the humidity buttons, removes heat from the incoming air.
Dependingon the position of the two blend flaps, the cold
air either passes directly to the vehicle outlet vents, or is
passed through the heater matrix to be reheated and then
to the vehicle outlet vents.
The amount of air passing through the heater matrix is
infinitely variable depending on ambienttemperature and
the temperature selected within the vehicle.
Selecting 'Climate Control' from the vehicle area menu,
will presentthetechnician with the dataloggertool selection

screen.

Details of the signals which may be monitored in the
system may be found in the DB7 Workshop Manual -
Section 8 - Air Conditioning'
Anti-Lock Braking Diagnostics
The Teves Mk IV Braking System consists of two sub­
systems, power braking and anti-lock braking.
The PDU software(DataLogger) only allows the monitoring
of the anti-lock braking system.
The ABS System consists of:
Four wheel speed sensors.
One control module.
Seven solenoid valves.
One pressure switch.
One fluid level switch.
The ABS System
is
controlled and continuously monitored
by the ABS control module, which automatically
switchesoffthesystemifafailure is identified, illuminating
a warning lamp and leaving
full,
boosted braking to all
wheels. A wheel speed sensor is installed at each wheel.
Their wheel speed related signals are processed by the
control module, which triggers the solenoid valves to
modulate hydraulic pressure, preventing the wheels from

locking.
The control module also monitors the fluid
level and will inhibit ABS operation should lowfluid level
be detected.
The Datalogger function will permit monitoring of the
complete system apart from the solenoid valves. The
control module transmits short duration test pulses of 25
to 100 microseconds to the solenoid valves. These
pulses are too fast for the PDU to monitor and as a result
would cause confusing waveforms.
Selecting 'Anti-Lock Braking' from the vehicle area menu,
will present the technician with the following menu of
diagnostic tools screen:
Anti-Lock Brakes Diagnostic
Datalogger
Diagnostic Trouble Codes
o
ABS Diagnostic Trouble Codes
The DTCs which are supported in the Teves Mk IV ABS
system are listed in the workshop manual - Section 5
Brakes Wheels and Tyres.
September 1996 9-43

The Aston Martin Lagonda Diagnostic System
Users Guide
Em^'^?

ABS Datalogger
The following signals in the Teves Mk IV ABS system may
be monitored using the datalogger function.
DTCs Number of DTCs Logged
The Diagnostic status manager (DSM) receives and
processes fault information and decides when a DTC
should be logged and the MIL turned on. The actual total
stored is indicated by the parameter.
FBRAKE Brake Switch
The signal from the brake switch is used by the CM to
ensure that traction control is inhibited when the brakes
are applied. The input circuitry within the CM is a
1
OK
pull-up to ignition voltage. When the switch is closed the
parameter is set to 1.
FLWS Front Left Wheel Speed Sensor
An indication sensor outputs a sinusoidal wave form 48
pulses per revolution. The output is processed by the CM
to control braking and traction. The sensor is continually
monitored for open and short failure and operating range.
If its output exceeds 330km/h it is deemed to be faulty and
the CM is disabled. The parameter tracks the sensor
weaveform through 255 steps.
FRWS Front Right Wheel Speed Sensor
An indication sensor outputs a sinusoidal wave form 48
pulses per revolution. The output is processed by the CM
to control braking and traction. The sensor is continually
monitored for open and short failure and operating range.
If its output exceeds 330km/h it
is
deemed to be faulty and
the CM is disabled. The parameter tracks the sensor
weaveform through 255 steps.
RLWS Rear Left Wheel Speed Sensor
An indication sensor outputs a sinusoidal wave form 48
pulses per revolution. The output is processed by the CM
to control braking and traction. The sensor is continually
monitored for open and short failure and operating range.
If its output exceeds 330km/h it
is
deemed to be faulty and
the CM is disabled. The parameter tracks the sensor
weaveform through 255 steps.
RRWS Rear Right Wheel Speed Sensor
An indication sensor outputs a sinusoidal wave form 48
pulses per revolution. The output is processed by the CM
to control braking and traction. The sensor is continually
monitored for open and short failure and operating range.
If its output exceeds 330km/h it is deemed to be faulty and
the CM is disabled. The parameter tracks the sensor
waveform through 255 steps.
Passive Anti Theft (PATS) Diagnostics
Security System Diagnostics
Becauseof the requirementto maintain vehicle security,
the PATS and Security System operating instructions
and diagnostics are covered in the Vehicle Security
supplement to section 6 of the workshop manual. This
supplement has restricted circulation and is only
available to Aston Martin Dealers.
9-44 September 1996

^7
The Aston Martin Lagonda Diagnostic System
Users Guide
Diagnostic Trouble Codes
Introduction
The 'Diagnostic trouble codes' application enables the
PDU to monitor the trouble codes logged in selected
control module's and provides the following functions:
• Decode and display any trouble codes logged by
the control module(s) being monitored.
• Decode and display enhanced diagnostic
information, together with any count of the number
of occurrences, when supported by the control
module(s).
• Clearsomeorallofallthesetroublecodes selected
by the user on the PDU screen, when supported by
the control module(s).
Diagnostic Trouble Codes are logged by the Engine
Management and by the Automatic Transmission control
units and can be accessed using the PDU. Logged codes
in the 95 MY Teves Mk II ABS controller can only be
accessed using the brake warning light. The Air
Conditioning control unit does not log trouble codes.
Operation
From the Main Menu make the following selections:
Select Diagnostics
Select Engine or Transmission
The system will then load the appropriate
software
Select Diagnostic Trouble Codes
Connect the PDU to the car as shown on the
screen diagram
Select the / icon to confirm connection
The PDU will then interrogate the chosen control
unit and will display any logged trouble codes.
If no trouble codes have been flagged by the control
module, the PDU will display a screen similar to Fig. 15
The trouble code screen will be headed by a module title
block followed by a list showing all logged trouble codes
for the seleaed module.
Note: There may be more logged diagnostic trouble
codes than displayed on the first
screen.
Use the 'up
arrow' and 'down arrow' icons if
necessary
to scroll
through the total display.
On the Zytek engine management system only, each
trouble code definition will be individually selectable to
invoke the clear trouble codes screen. If one or more
trouble codes are selected, the clear all and clear selected
trouble code icons will be displayed.
On all other systems, only the 'Clear All' function is
available.
'Clear All' and 'Clear Selected Codes' Icons
Freeze Frame Data
m*
As any engine management trouble code is

logged,
the system takes a snapshot (freeze
frame) and records the state of all signals at
that time.
On the Zytek engine management system (95 MY), freeze
frame data can be displayed by selecting a logged trouble
code and touching the 'snowflake'
icon.

On the 97 MY EEC V engine management system, freeze
frame data is accessed using the OBD II scan
tool.

ECC-V EMS DTC'S
No fault codes present
l^
D
a
El
The No Fault Codes screen
September 1996 9-53

"^I?
The Aston Martin Lagonda Diagnostic System
Users Guide
Datalogger
Introduction
Datalogger is software produced to identify permanent or
intermittent faults on vehicle electronics. The objective of
Datalogger is to provide a view of the vehicle's electrical
behaviour, such that intermittent activity can be recorded
and interpreted quickly and accurately. Running on the
Portable Diagnostic Unit (PDU), the Datalogger
appi ication can captu
re
vehicle information in three ways.
• Serial communications direct from the control unit.
• Parallel communications using the Interface Adaptor.
• Direct signal monitoringusingthemeasurementprobes.
Serial Communication
Serial Communication is a two-wire communication link
between the PDU and most vehicle control modules
providingdigital measurements forconnected components.
The serial communication link allows the tester to
determine the current condition of components connected
to the control module, and to identify any history of faults.
On later vehicles, the PDU is connected to the vehicle
diagnostic sockets via the mu
Iti
Protocol Adaptor (MPA) to
gather serial data from the control modules.
Parallel Communication
The Vehicle Interface Adapter (VIA) provides an interface
between the PDU and the vehicle harnesses for the
acquisition of multiple analogue measurements. The VIA

is
connected between the relevantvehicle control module
and it'sharness connector. Thisallows the PDU to captu re
information from a multitude of channels entering the
control module. This vehicle interface is used with control
modules not equipped with a serial communication link
(Teves Mk II braking system and the air conditioning
system).
Measurement Probes
The measurement probes permit readings to be taken
directly from any connector on the vehicle.
Datalogger Applications
Datalogger may be used to interrogate the following DB7
systems:
• ABS braking system controller
• Engine Management Controller
• Air Conditioning Controller
• Automatic Transmission Controller
• Passive Anti Theft (97 MY)
• Security System (97 MY)
Using the Datalogger
Configure the vehicle to the normal operating conditions
for the system under test.
From the PDU main menu screen:
Highlight 'Diagnostics'.
Press the 'tick' icon to confirm the selection.
Enter the Transmission Type and confirm the selection.
Select the Vehicle Area to be tested and confirm the

selection.

The PDU tools screen should now be displayed.
Highlight 'Datalogger'.
Confirm the selection with the 'tick'
icon.

The PDU connection screen should now be displayed.
Cable Setup
Upper Diagnostic Socl<et
o
PD\J Connections for Datalogger
Connect the PDU to the vehicle as described in the screen

image.

Switch On the ignition and press the 'tick'
icon.

September 1996 9-55