1997 ASTON MARTIN DB7 lock

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Air Conditioning
System Description
System Description
The in-car temperature and humidity are regulated by the electronically controlled air conditioning system. The
system comprises four subsystems:
• heater matrix, supplied with water from the engine cooling system
• refrigeration
• vacuum
• electronic control
Apart from the ambient temperature sensor and the aspirated in-car temperature sensor, most of the components
are housed in the air conditioning unit (Fig. 1) situated behind the dash board, or in the engine compartment.
Figure 1.
Key to Fig. 1 - Left Hand Air Conditioning Unit

1.
Upper feedback potentiometer

2.
Water temperature switch
3. Lower feedback potentiometer

4.
Vacuum valve block
5. Vacuum restrictor
6. Condensate drain tube
Figure 2.
Key to Fig. 2 - Right Hand Air Conditioning Unit

1.
Upper servo motor

2.
Electronic control module
3. Lower servo motor

4.
Evaporator sensor
5. Condensate drain tube
Special Servicing Tools and Equipment
1 PDU system
1 Charging station
1 Leak detector
1 Temperature test box
1 Sanden compressor service tool kit
1 CM Type compressor service tool kit
1 Digital voltmeter
1 Multimeter
May 1996 8-7

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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

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Air Conditioning
System Trouble Shooting
System Trouble Shooting
There are five basic symptoms associated with air conditioning fault diagnosis. It is very important to identify the area of
concern before starting a rectification procedure. Spend time with your customer on problem identification, and use the
following trouble shooting guide.
The following conditions are not in order of priority.
No Cooling

1.
Is the electrical circuit to the compressor clutch functional?

2.
Is the electrical circuit to the blower motor(s) functional?
3. Slack or broken compressor drive belt.

4.
Compressor partially or completely seized.
5. Compressor shaft seal leak (see 9).
6. Compressor valve or piston damag^ (may be indicated by small variation between HIGH & LOW side pressures
relative to engine speed).
7. Broken refrigerant pipe (causing total loss of refrigerant).
8. Leak in system (causing total loss of refrigerant).
9. Blocked filter in the receiver drier.

10.
Evaporator sensor disconnected?

11.
Dual pressure switch faulty?
Note:
Should a
leak or low
refrigerant be established as
the
cause,
follow
the procedures
for
Recovery-Recycle
-Recharge,
and
observe all refrigerant and oil handling instructions.
insufficient Cooing

1.
Blower motor(s) sluggish.

2.
Restricted blower inlet or outlet passage
3. Blocked or partially restricted condenser matrix or fins.

4.
Blocked or partially restricted evaporator matrix.
5. Blocked or partially restricted filter in the receiver drier.
6. Blocked or partially restricted expansion valve.
7. Partially collapsed flexible pipe.
8. Expansion valve temperature sensor faulty (this sensor is integral with valve and is not serviceable).
9. Excessive moisture in the system.

10.
Air in the system.

11.
Low refrigerant charge.
May 1996 8-17

Air Conditioning
/J=y>f^^^
—p )
System Trouble Shooting

12.
Compressor clutch slipping.

13.
Blower flaps or distribution vents closed or partially seized.

14.
Water valve not closed.

15.
Evaporator sensor detached from evaporator.
Intermittent Cooling
Is the electrical circuit to the compressor clutch consistent?

2.
Is the electrical circuit to the blower motor(s) consistent?
3. Compressor clutch slipping.

4.
Faulty air distribution flap potentiometer or motor.
5. Motorised in-car aspirator or evaporator temperature sensor faulty, causing temperature variations.
6. Blocked or partially restricted evaporator or condenser.
Noisy System

1.
Loose or damaged compressor drive belt.

2.
Loose or damaged compressor mountings.
3. Compressor oil level low, look for evidence of leakage.

4.
Compressor damage caused by low oil level or internal debris.
5. Blower(s) motor(s) noisy.
6. Excessive refrigerant charge, witnessed by vibration and 'thumping' in the high pressure line (may be indicated by
high HIGH & high LOW side pressures).
7. Low refrigerant charge causing 'hissing' at the expansion valve (may be indicated by low HIGH side pressure).
8. Excessive moisture in the system causing expansion valve noise.

Note;
Electrical faults
may
be more rapidly traced using PDU.
Insufficient Heating

1.
Water valve stuck in the closed position.

2.
Motorised in-car aspirator seized.
3. Blend flaps stuck or seized.

4.
Blocked or restricted blower inlet or outlet.
5. Low coolant level.
6. Blower fan speed low.
7. Coolant thermostat faulty or seized open.
8-18 May 1996

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Air Conditioning
In Car Controls
In Car Controls
Temperature Demand Switch
In-cartemperatu
res are selected by
the temperature
demand switch (Fig. 1).
Face Level Differential Controller
The face level differential control alters the
temperature of the air distributed through the face
level vents. The switch is coupled to a 10 K ohm
potentiometersupplied with+5 volts
from
pin 43 of
the control module
(Fig.
3). Temperature, from the
face
vents,
is
decreased by moving the switch
anti­

clockwise and increased by moving it clockwise.
6.6 K
lOKQ
Linear
+ 5v
7 Temperature
Differential Signal
10CND
Figure 1.
The switch is coupled to
a
590 ohm potentiometer

(Fig.
2) supplied with +5 volts from pin 43 of the

ECM.
The output voltage
is
from zero to
2.885
volts
which represents a range of temperatures from 16
to 38°C. Rotation of the switch is restricted
mechanically to 180° of travel.

Figure
3.
590 Q Linear
1 GND
.2 Temperature Demand Signal
•3 +5v
410 Q

Figure
2.
May 1996 8-21

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Air Conditioning
Upper Feedback Potentiometer / Servo Motors
Upper Feedback Potentiometer
The upper feedback potentiometer determines the
position of the upper blend flap in the air
conditioning unit and feeds this information to the
ECM enabling it to command the upper flap servo
motor to move the flap to a new position and
maintain the desired temperature of the air at the

dashboard,
centre, screen and side demist vents.
Servo Motors
Lower Servo Motor
The lower blend flap assembly has two inlets and a
single outlet which are wholly or partially blocked
by the flap to control the temperature of air entering
the lower half of the vehicle.
V 1
-•2
V3 -•2

Figure
2.

1.

2.

3.
+5 volts from ECM Pin 43
Feedback signal to ECM Pin 30
Earth-Ground
The potentiometer is supplied with +5V from pin
43 of the ECM and returns its feedback signal via
pin 30. The feedback signal is
1
OOmV (COLD AIR)
to 1.9V (HOT AIR).
Figure L

1.
Energising voltage Lower Servo ECM Pin 37
(Upper ECM 40)

2.
Energising voltage Lower Servo ECM Pin 41
(Upper ECM 42)
A servo motor
(Fig.
1) drives the lower blend flap to
the desired position via a 1500:1 reduction gear
box. The motor is bidirectional and energised from
pins 37 and
41
of the
ECM.
The energising voltages
have the following values: LOW ± O.OV to 2.0V;
HIGH± 7.0V to 9.5V.
Upper Servo Motor
The upper servo motor (Fig. 1) drives the upper
blend flap to the desired position through a 1500:1
reduction gearbox. Like the lower servo motor it is
bi-directional and energised by the ECM (pins 40
and 42). The energising voltages are:
LOW + O.OV to 2.0V
HIGH + 7.0V to 9.5V.
May 1996 8-27

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Air Conditioning
Sanden Compressor SD7H15
Sanden Compressor SD7H15
The Sanden SD7H15 compressor
is a 7
cylinder
machine with
a
bore
of
29.3
mm (1.15 in) and a

stroke
of
32.8
mm (1.29
inches).
The displacement
per
revolution
is
155cc
(9.5

cubic inches).
The magnetic clutch
is
engineered with
the

compressor
as a
complete assembly resulting
in a

relatively small unit
of
lightweight construction.
The compressor may be mounted up to 90° from
its

upright position.
The compressor incorporates
a
lubrication system
which reduces the
oil
circulation ratio
to a
level
of

less than
2% at 1800 rpm.

An
oil
deflector
and
positive pressure differential
lubrication system promotes oiling
to the
cylinder

wall,
piston
rod
assemblies, main bearings
and

shaft
seal,
and
ensures that
oil
circulation
to the

refrigeration circuit
is
kept
to a
minimum.
The

compressor ischarged
with!
35 cc(4.6fluid ounces)
ofSunico NoSGSoil at the factory. Only this oil
or

oneoftheequivalentoilsdetailed below should
be

used.

Key

1.

2.

3.
4.
5.
6.
7.
8.

9.
10.

11.

12.
13.
14.
15.
16.

to Fig. 2.
Service port
Cylinder head
Hose connection
Anti-rotation gear
Oil filler plug
Planet plate
Clutch bearing
Electromagnetic clutch
Valve plate assembly
Cylinder and valve plate gasket
Cylinder block
Piston
Cam rotor
Needle thrust bearing
Front housing and 'O' ring
Shaft seal
Compressor Oils
Suni
CO
No 5GS
Texaco Capella E
Virginia Chemicals 500 Viscosity

13
14 15 16

Figure
2.

May
1996
8-37

Air Conditioning
Manifold Gauge Set 5=2?
Manifold Gauge Set
The manifold gauge set is a most important tool for
fault diagnosis and system efficiency assessment.
The relationship to each other of HIGH and LOW
pressures and their correlation to AMBIENT and
EVAPORATOR temperatures must be compared to
determine system status. Because oi the heavy
reliance upon this piece of equipment for service
diagnosis, ensure that the gauges are calibrated
regularly and the equipment is treated with care.
BLUE LOW SIDE RED HIGH SIDE
LOW

m
m

Manifold.

The manifold is designed to control refrigerant
flow. When connected into the system, pressure is
registered on both gauges at all times. During
system tests both the high and low side hand valves
should be closed (rotate clockwise to seat the
valves). The hand valves isolate the low and the
high sides from the centre (service) hose.
Low Side Pressure Gauge.
This compound gauge
is
designed to register positive
and negative pressure and may be calibrated as
follows:
• Full Scale Deflection - 0 to 24 bar pressure
in a clockwise direction
• Otol bar FSD negative pressure in a counter
clockwise direction.
High Side Pressure Gauge.
This pressure gauge may be calibrated from 0 to 34
bar FSD inaclockwisedirection. Depending on the
manufacturer, this gauge may also be of the
compound type.
Figure 1
The gauge set (Fig. 1) consists of a manifold fitted
with:

1 Low side service hose - BLUE.
2 Low Side hand valve - BLUE.
3 Low pressure compound gauge - BLUE.
4 High pressure gauge- RED.
5 High Side hand valve - RED.
6 High side service hose - RED.
7 System service hose - NEUTRAL COLOUR
(commonly yellow).
8-38 May 1996