1997 ASTON MARTIN DB7 cooling

Air Conditioning
System Checking with the Manifold Gauge Set ffi:S5=27
After making the above checks operate the system
and check the performance. If the Condition is not

rectified.

1.
inspect the system for overcharge of refrigerant and
rectify as follows.
A. Discharge the system, until a stream of bubbles
appear in the sight glass and both gauge readings
drop to below normal.
B. Add new refrigerant until the bubbles disappear
and the pressures are normal. Then add 0.25 to 0.5

lb.
of additional refrigerant.

2.
Operate the system and check the performance.
If the gauge readings are still too
high.

3. Depressurise the system.
3. Removeand inspectthecondenserforoilclogging.
Clean and flush the condenser to ensure the free
passage refrigerant or renew the condenser.

4.
Renew the receiver-drier.
5. Evacuatethesystem using
a
vacuum pump Recharge
the system with new refrigerant. Operate the system
and check the performance
Moisture in the System
Complaint.
Cooling notadequateduringthe hot part of theday.
Note: Cooling may
be satisfactory
during
early
morning/

late evening
but
inadequate
during
the
hot part of
the
day.

BLUE LOW SIDE RED HIGH SIDE

1.

2.

3.

4.

5.
LOW
Condition.
The low side gauge reading normal but may drop
into vacuum during testing.
The high side gauge reading normal but drops
when the low side drops into vacuum. The sight
glass may show tiny bubbles.
The discharge air from the evaporator is cold but
becomes warm when the low side gauge drops into

vacuum.

Diagnosis.
Excessive moisture in the system.
Desiccant agent saturated with moisture which is
released during high temperatures. The moisture
collects and freezes in the expansion valve which
stops the refrigerant flow.
Correction.
Depressurise the system.
Renew the drier bottle.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
Operate the system and check the performance.
8-44 May 1996

=2?
Air Conditioning
System Checking with the Manifold Gauge Set
A Large Amount of Air in the System.
Complaint.
Little or no cooling.

1.

2.

3.

4.

5.

BLUE
LOW SIDE RED HIGH SIDE
Condition.
The low side gauge reading is too
high.
The high
side gauge reading is too
high.
An occasional
bubble in the sight
glass.
The discharge air from the
evaporator is not
cool.

Diagnosis.
Air in the system. The refrigerant contaminated by
non-condensables (air and/or moisture).
Correction.
Depressurise the system.
Renew the receiver-drier.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
Operate the system and check the performance.
Expansion Valve Malfunction.
The valve stuck open.

1.

2.

3.

4.

5.
6.
BLUE LOW SIDE
HIGH
Complaint.
Little or no cooling.
Condition.
The low side gauge reading is too
high.

The high side gauge reading is normal or slightly
low.
The discharge air from the evaporator is warm. The
suction hose and the evaporator show signs of
heavy sweating.
Diagnosis.
The expansion valve allowing excessive flow of
refrigerant through the evaporator coils causing
flooding of the coils.
Correction.
Depressurise the system.
Renew the expansion valve.
Renew the drier bottle.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
Operate the system and check the performance.
May 1996 8-45

Air Conditioning
System Checking with the Manifold Gauge Set ^^?
Expansion Valve Malfunction
The valve stuck closed.
Restriction in the High Pressure Side.
BLUE LOW SIDE SED HIGH SIDE
Complaint.
Cooling is not adequate.
Condition.

1.
The low gauge reading is too low (0 or a vacuunn).

2.
The high side gauge reading is too low.
3. The discharge air from the evaporator only slightly

cool.

4.
The expansion valve shows signs of heavy sweating
or frost.
Diagnosis.
The expansion valve restrictingthe refrigerant flow.
Correction.

1.
Depressurise the system.

2.
Renew the expansion valve.
3. Renew the drier bottle.

4.
Evacuate the system using a vacuum pump.
5. Recharge the system with new refrigerant.
6. Operate the system and check the
performance.

1.

2.

3.

4.

1.

2.

3.

4.

5.
BLUE LOW SIDE
Complaint.
Cooling is not adequate.
Condition.
The low side gauge reading is low.
The high side gauge reading builds up to an
excessively high reading.
The discharge air only slightly
cool.

The high pressure liquid hose from the drier bottle
to the evaporator is cool to the touch or shows signs
oi heavy sweating or frost.
Diagnosis.
A restriction in the receiver-drier orthe high pressure
liquid hose from the drier bottle. Which results in
the compressor removing refrigerant from the
evaporator faster than it can enter. This results in a
starved evaporator.
Correction.
Depressurise the system.
Renew the drier bottle and/or the high
pressure liquid hoses or other defective parts.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
Operate the system and check the performance.
8-46 May 1996

Air Conditioning Repair Procedures
Air-Conditioning Unit Renew ^^?

10.
Disconnect the pliable trunking from the unit (Fig.
8.2.02.1
EvaporatOr Unit Renewal
1-2). ^

1.
Remove the air conditioning unit assembly.

2.
Remove the heater pipe guide plate securing screws
and remove the guide plate.
3. Remove the screws secu ri ng evaporator sensor and
withdraw the sensor from the evaporator.

4.
Remove the screws securing the solenoid mounting
plate and displace the mounting plates from the
unit.
5. Removetheharnesstocasingearthboltand displace
the harness.
6. Cut and remove the harness to casing securing
ratchet straps and displace the harness from the

casing.

7. Displace the vacuum hose from the casing.
8. Displace and remove the casing securing clips.
9. Splitthecasingandremovetheevaporatorfromthe
unit.

10.
Remove the expansion valve guide securing screws
and remove the plate.

11.
Displace and remove the plate from the evaporator.

12.
Fitting the new evaporator is the reversal of the
removal procedure.

13.
Refill the engine cooling system with coolant.

14.
Recharge the air conditioning system.
Figure 1

11.
Twistandpulloutthefourairconditioningunitstub
pipes (Fig. 1-3)

12.
Remove the screws securing the air conditioning
unit support stays.

13.
Displace the tunnel carpet for access to the lower
fixing bolts and remove the stays.

14.
Disconnect the condensate drain tubes.

15.
Peel off the tape securing the windscreen demist
duct to the distribution box (Fig.
1
-4).

16.
Remove the air conditioning unit to bulkhead
securing nuts.

1
7. Carefully lift out the air conditioning unit complete
with the distribution box.

18.
Remove the distribution box securing screws and
remove the assembly (Fig.
1
-5).

19.
Reverse the removal procedure to refit the air
conditioning unit.

Note:
Ensure new'O'rings
are
fitted toall air conditioning
tiose connections.
8-56 May 1996

^=2?
Air Conditioning
Portable Diagnostic Unit - Signal Definitions
ThefollowingsignalsaresupportedontheAir-ConditioningControlModule. For each signal. The signal name, mnemonic
and background information are detailed.
Ambient Temperature Sensor
(AMBTEMP)
Auto-Recircuiation Input
(ARECIP)
Auto-Recirculation Output
(ARECOP)
Auxiliary Battery Positive
(AUX+)
Clutch Relay Drive Output
(CLUREL)
A/CCM Pin 34 ref Pin 6
This sensor is located in the right hand blower motor. This signal is used to enable
the A/C system to compensate for changes in ambient air temperature. The output
to pin 34 is 2.732 volts at 0 degrees Celsius and changes by 0.01 volts for each
degree Celsius above or below zero.
A/CCM Pin 9 ref Pin 6
This is effectively an On/Off switch for the A/C system and forms part of the fan
control switch.
Switch Off - Pin 9 should be at ground
Switch On - Pin 9 should be at 10+ volts.
When pin 9 is at ground, pin 3 will be at 10+ volts causing the recirculation flaps
to open.
A/CCM Pin 3 ref Pin 6
This signal will cause the recirculation flaps to close. Operating conditions should

be:

A/C Off - 10+ volts at pin 3, flaps open.
Temp demand minimum - 10+ volts at pin 3, flaps open.
Defrost - 0 volts at pin 3, flaps closed.
Temp demand max - 0 volts at pin 3, flaps closed.
A/CCM Pin 1 ref Vehicle Battery -ve
This signal istheauxiliary supply to the A/CCM. Pin
1
should read battery voltage
if the ignition switch is in the auxiliary or ignition on positions. Pin
1
should read
0 volts when the ignition switch is in the Off position or in position III whilst
cranking the engine. Loss of this supply will cause total failureof the A/C system.
A/CCM Pin 20 ref Pin 6
This signal responds to the input at pin 5 (evaporator sensor). When pin 5 is
between 2.715 and 2.725 volts, pin 20 should read below 1 volt, and the
compressor clutch will be switched off. When pin 5 is between 2.735 and 2.745

volts,
pin 20 will rise to 10+ volts and the compressor will re-engage.
Centre Vent Solenoid
(CVSOL) A/CCM Pin 18 ref Pin 6
The centre vent solenoid controls the operation of the centre vent flap. The centre
vent will open to increase the cooling capabilities of the vehicle when cooling is

selected.
In all other conditions, the centre vent will be closed.
Solenoid energised: pin 18 should read 10+volts and the centre vent will be open.
Solenoid de-energised; pin 18 should read below 0.5 volts and the centre vent
should be closed.
May 1996 8-67

3^7?
Air Conditioning
Portable Diagnostic Unit - Signal Definitions
Fanspeed Medium
(FANMED)
Five Volt Supply
(FIVEV)
Flap Servo Drive Signals
Lower Servo Forward Drive
(FORSERL)
Upper Servo Forward Drive
(FORSERU)
Lower Servo Reverse Drive
(REVSERL)
Upper Servo Reverse Drive
(REVSERU)
Ground Voltage
(GND10)
A/CCMPin 14ref Pin6
This signal is generated from the fanspeed control switch.
Switch at Low, pin 14 should read 0.6 volts.
Switch at Off, L, H or D positions, pin 14 should read 3.6 ±0.8 volts.
A/CCM Pin 43 ref Pin 6
This 5 volt rail provides the power supply for all the sensors and the feedback
potentiometers. Any variation in this signal would totally upset the balance of the
whole system.
The servo drive signals control the position of the upper and lower
flaps.
The drive
signals work in pairs, two for the upper and two for the lower flaps.
A/CCM Pin 37 ref Pin 6
A/CCM Pin 40 ref Pin 6
A/CCM Pin 41 ref Pin 6
A/CCM Pin 42 ref Pin 6
When the flaps are stationary, all signals will be at 0.6 volts approximately. When
the flap(s) is being driven, the drive iine(s) will rise to approximately 6 volts.
As the flap approaches its final position, the drive signal will be pulsed to nudge
the flap to the exact position required.
Note: If
a
drive
signal rises to above
8.5
volts
and
the servo
motor
does
not
operate,
suspect

an open circuit within the servo.
A/CCM Pin 10 ref Pin 6
This is the ground supply from the A/CCM to the in-car sensor and should read
below 10 millivolts.
Failure of this line will cause the in-car sensor to believe the vehicle temperature
to be at maximum all the time, thus forcing the system into permanent cooling.
Under these circumstances, pin 4 (in-car sensor output) will be approximately 5

volts.

May 1996 8-69

O" D'^?
Air Conditioning
Portable Diagnostic Unit - Signal Definitions
Reference Signal
(REF) A/CCM Pin 7 ref Pin 6
This is the main reference signal for the A/CCM. All the sensors reference against
this voltage. Drift in this signal will cause inconsistent temperature control.
Normal voltage should read 2.885 ±10 millivolts
Temperature Demand
(TEMPDEM)
Temperature demand control either selects the required temperature of the system
(auto mode) or the outlet temperature of the vents (manual mode). Pin 35 will vary
from 0 volts at full cooling up to 2.885 volts at full heating.
Note: When
defrost is
selected,
the
signal at pin 35
is
ignored.
The system
will go into full
heating through the upper flaps
only.

Upper Servo Feedback Potentiometer
(USERFB) A/CCM Pin 30 ref Pin 6
The feedback signal informs the control module ofthe exact position of the flaps,
enabling accurate control ofthe flap position.
Defrost - Lower flap signal should read 2.9 volts (flap closed, the upper flap
signal should read 1.9 volts.
Max Temperature - Lower flap signal should read 1.14 volts, upper flap signal
should read 1.9 volts.
Min Temperature - Both upper and lower flap signals should read
1
30 ±80
millivolts.
Note: If the
feedback sticks
low, with the
fan
continually running,
suspect an
open circuit
in the 5 volt supply to the feedback potentiometer or the potentiometer itself
Water Switch
(WATSW)
Water Valve
(WATVAL)
A/CCM Pin 21 ref Pin 6
The water switch monitors the temperature ofthe coolant and inhibits heating by
restricting fan operation at coolant temperatures below 30 degrees Celsius. This
enables the vehicle to warm up at a faster rate. It can be overridden by selecting
Defrost.
A/CCM Pin
1
7 ref Pin 6
The water valve controls thef low of hot coolant to the heater matrix. When manual
full cooling is selected, the valve will close inhibiting the heating effort ofthe
matrix, thus enhancing the cooling effect
Full cooling selected; pin
1
7 should read 10+volts and the water valve should be

closed.

All other conditions, pin
1
7 should read below 0.5 volts and the water valve should
be open.
May 1996 8-73

The Aston Martin Lagonda Diagnostic System
Installation Instructions ^7
Base Station installation
It is recommended that the base station is wall
mounted (Fig 3). Alternatively it may be mounted
on a bench. The base station houses the CD-ROM
drive and power supplies.
Note: The electronic module should only be fitted
after

the base station has been installed.
Wall Mounting
It
is
importantthatthefollowing points be considered
before carrying out the mounting procedure.
The location should be close to the vehicle repair

bays.
The base station will require a power outlet
close by, such that the 2m mains lead will
comfortably reach the outlet.
Thewall plate should be attached with fourfasteners,
each of which has a minimum pull-out strength of
300 kg (662 lb). Thefourfasteners are not supplied,
as the type of fastening will depend on the wall

material.
The mounting holes in the wall plate are
8mm diameter with a maximum clearance for a
socket spanner of 30mm. It is recommended that
6mm diameter bolts are used to secure the wall

plate.

WARNING: The mains power outlet must be dose
to the equipment and be clearly recognisable as
the power source for safety reasons.
French Market
Only:
Do not connect the PDU
equipment
to
IT(lmpedante Terre) power systems.

r

900mm
Figure 3. Wall Mounted installation
WARNING: This equipment must be earthed via
the
mains
lead through the outlet socket. In markets
where three pin main power outlets are not
available, a separate earth point must be used
Procedure

1.
Select a suitable location.

2.
Mark a horizontal line on the wall 900mm above
the floor (Fig 3)
3. Removethetwoscrewssecuringthewall mounting
plate to the base station and remove the wall
mounting plate.

4.
Holdthewall mounting plate up to the marked line
and mark four hole positions for the wall mounting
plate bolts.
5. Drill the wall to the correct diameter and depth
required for the four bolts.
6. Securely fasten the wall mounting plate to the
wall.

Lift the base station onto the wall mounting plate,
fit and tighten the two screws/washers to secure the
base station to the mounting plate.
CAUTION: The gap beneath the base station
should be maintained free from obstructions to
allow a flow of air under the unit for cooling.
9-8 May 1996