low oil pressure ASTON MARTIN DB7 1997 Workshop Manual

Electrics
Component Index Sheet 3 - 97
MY

Component
Name
Interior Light - Rear RH
Key Solenoid
Key-In Warning Switch
Low Coolant Signal Transmitter
Low Level Sensor (Screenwash)
Map Reading Light
Mass Airflow (MAF) Sensor
Multifunction Module
Number Plate Lamp - LH
Number Plate Lamp - RH
Oil Pressure Transducer (EOP)
PATS Module
PATS Transceiver
Performance Mode Switch
Powertrain Control Module (PCM)
Purge Cannister Vent Valve
Radiator Switch
Radio
Radio Aerial
Radio Telephone Connector
Radio Tweeter (LH)
Radio Tweeter (RH)
Rear Lamp - LH
Rear Lamp - RH
Relay - Air Conditioning
Relay - Air Conditioning W.O.T.
Relay - Air Pump
Relay - Auxiliary Load (
Relay - Auxiliary Load (
Relay - Courtesy Lights (
Relay - Clutch (
Relay-Day Time Running (
Relay - Drivers Seat Heater (
Relay - Fan Change-Over (
Relay - Fan Run On
Relay - Front Fog Lamps
Relay - Fuel Pump 1
Relay - Fuel Pump 2
Relay - Gearbox Failure Warning
Relay - Glass Drop
Relay - Hazard Unit
Relay - Headlamp Dipped Beam
Relay- Headlamps
Relay - Heated Front Screen Control
Relay - Heated Rear Window
Relay - Hood Down (Roof Down)
Relay - Hood Up (Roof Up)
Relay - Horn
Relay - indicator Unit (Flasher Unit)
Relay - Left Quarter Light Up
Relay - Left Quarter Light Down
Relay - Load
Relay- Main
Relay - Main Beam
Relay - Passenger Seat Heater
Component
Location
14-6
14-4
14-4
7-13
14-3
10-9
14-1
6-1
14-8
14-7
15-3
4-9
15-4
6-8
4-1
15-7
15-2
5-1
5-4
8-3
5-2
5-2
15-8
15-6
see relay location chart) di II II II
II II II II
II II II II
11 II II II
II II II II
II II II II
II II II II
II II II II
II II II II
11 II II II
II II II II
II II II II
II II It II
II II II II
11 II II II
II II II II
II II II II
II II II II
II II II II
II It II II
II II II II
11 II II II
II II II II
11 II II II
11 II II II
II II II II
II II II II
II II II II
II II II II
II II II II
Circuit
Reference
16-A2
9-D3
9-D3
12-82
3-A2
8-A4
5-D2
12-B5
16-D6
16-C6
5-C4
12-B1
9-C2
4-A2
6-B5
15-B3
5-D1
10-B3
16-C2
16-B5
8-A3
12-C2
15-B6
16-D2
3-A4
3-A5
1-A5
9-D1
12-D1
9-D1
1-B5
1-A6
23-D3
3-C4
3-A3
) 1-B5
) 17-A2
) 17-A4
9-D2
) 12-C1
) 8-C3
2-A2
) 2-B2
) 12-D3
) 8-C4
) 19-A2
) 19-A3
) 1-85
) 8-C3
) 18-A5
) 18-A5
) 12-D1
) 12-D2
) 2-83
) 24-D3
September 1996 6-45

^"^
Body and Trim
Body Repair
Precautions
Paint
Ensure that there is efficient ventilation at all times. Paint spraying should be confined to spray booths.
Anyone with a history asthma should not be engaged in any process which involves the use of isocyanates.
Any operator working inside a spray booth where isocyanates are present must use air-fed breathing equipment.
Supplied air to the visor should be fed at the recommended pressure and filtered to remove oil, water and fumes.
Operators involved in handling, mixing or spraying should wear protective clothing, gloves and goggles to avoid
skin and eye contact. A Paticle mask or canister typr respirator should be worn when sanding.
Applied heat
When welding, flame cutting or brazing and so on, goggles, a mask or fume extractor and flameproof protective
clothing should be used always.
It is especially important when working with polyurethane compounds to use air-fed breathing equipment.
Ensure that at all times the appropriate fire fighting equipment isavailableand that personnel are trained in its use.
Metal repair
Wear appropriate eye and hand protection when sanding, drilling, cutting, chiselling, flatting or welding. Wear a
face mask or air-fed visor when sanding or flatting either body solder or
fillers.
When a soldering operation has been

completed,
remove swarf from the work area and wash your hands thoroughly.
General Repair Notes
The following precautions should be noted before any work is carried out:
• disconnect the vehicle battery ground
lead,
taking note of the reconnection procedures
• Make sure that you have read and understood the safety related procedures in this section.
Caution:
Electric arc
welding must not
be
used on the
vehicle as the high
voltages produced by
this process
will
cause
irreparable

damage
to the electrical control and
microprocessor
systems.

All trim and electrical components in the locality of the repair must be removed or disconnected prior to panel
removal or replacement.
Welding and Gas Process Special Notes
Resistance spot welding, MIG welding and all gas processes may only be carried out on bare, unpainted or unplated

metal.
The flanges of panels, which are to be welded together, must be clean, corrosion free and treated as
appropriate with either weld-through or inter-weld sealer.
The resistance spot welding equ ipment used in vehicle repair does not always produce
a
weld of
equ
ivalent strength
to that produced in manufacturing. This means that a single row of spot welds should be spaced on a pitch of 19-
25 mm, which will usually result in more spot welds than found in the original factory joint.
Use a resistance spot weld cutter to remove resistance spot welds. Where a new joint is to be MIC welded, cut the
old resistance spot welds from the panel that is to be retained; the resulting holes are then used for plug welding.
Suitable holes may be drilled or punched as follows:
• 8.0 mm for sections up to 1.5 mm thickness
• 10.0 mm for thicker sections.
Always refer to the welding equipment manufacturers diagrams and tables for the relevant procedure.
May 1996 7-3

in:!M3^^?
Air Conditioning
Contents
Contents
General Description 8-5
Specifications 8-5
Climate Control System 8-6
System Description 8-7
Special Servicing Tools and Equipment 8-7
Working Practices 8-8
General 8-8
Handling Refrigerant 8-8
Handling Lubricating Oil 8-8
System Maintenance 8-8
Temperature Distribution System 8-9
Fan Speed Control (Mode Switch) 8-10
Face Level Temperature Differential 8-10
Temperature Rotary Control 8-10
Refrigeration Cycle 8-11
System Protection 8-12
General System Procedures 8-12
Leak Test 8-12
Charge Recovery (System Depressurisation) 8-12
Evacuating the System 8-13
Adding Compressor Lubricating Oil 8-13
Adding Refrigerant 8-14
Functional Check 8-15
System Trouble Shooting 8-1 7
Electronic Control Module (ECM) 8-19
In Car Controls 8-21
Temperature Demand Switch 8-21
Face Level Differential Controller 8-21
Air Conditioning Function Switch 8-22
Fan Speed Control Switch (Mode Switch) 8-23
Temperature Sensors 8-23
Evaporator Sensor 8-24
Motorised In-Car Aspirated Sensor 8-24
Water Temperature Switch 8-25
Blower Motors 8-25
Potentiometers 8-26
Servo Motors 8-27
Vacuum System 8-28
Pressure-Temperature Graphs 8-29
May 1996 8-1

Air Conditioning
Contents '=2?
System Fault Diagnosis
Fault Finding
Blower Motor Test
Open Water Temperature Switch Needs
Short Water Temperature Switch Leads
Refrigeration
Compressors
Compressor Clutch Control
Trinary Switch
Condenser
Receiver-Drier
Evaporator
Expansion Valve
Sanden Compressor SD7H15
Manifold Gauge Set
System Checking with the Manifold Gauge Set
Evacuating the Manifold Gauge Set
Connecting the Manifold Gauge Set
Stabilising the System
Purging the Test Hoses
Leak Test
Manifold Gauge Set Check Procedures
Refrigerant Slightly Low.
Refrigerant Excessively Low.
Air In The System.
Compressor Malfunction
Moisture in the System
A Large Amount of Air in the System.
Expansion Valve Malfunction.
Expansion Valve Malfunction
Restriction in the High Pressure Side.
Torque Levels for the Hose Connections
8-30
8-33
8-33
8-33
8-34
8-35
8-35
8-35
8-35
8-36
8-36
8-36
8-37
8-39
8-39
8-39
8-39
8-40
8-40
8-41
8-41
8-42
8-42
8-43
8-44
8-45
8-45
8-46
8-46
8-47
Air Conditioning Procedures
Depressurising
Recovering Refrigerant
Evacuating and Recycling the Refrigerant
Recharging the System
Compressor Oil Check
8-47
8-47
8-48
8-49
8-49
8-2 May 1996

Em^^^?
Air Conditioning
General Description
General Description
Specifications
Refrigerant
Designation
Refrigerant R134A

(HFCUAA)

Compressor
Type
&
model
SD-7H15
Charge weight
1050g±50g
Configuration
7 cylinder
Compressor Lubricants
Designation
Polyalkylene glycol
(PAG)

Standard
for
Recovery, Recharge
and
Recycle Equipment,
System Capacity
120-150
ml

Manufacturer and Type
ICI Klea
or
equivalent

Manufacturer

Sanden
155 cm^
per
revolution
Manufacturer and Type
Sanden SP
20

Feature

Recovery rate
Cleaning capability
Oil separator
Vacuum pump
Filter

Charge

Hoses
Charge pressure
Compressor Belt Tension
Type
Vee belt
Burroughs method
Clavis method
Requirement

0.014-0.062
mVmin.
(1.36 kg in 20
minutes)
15
ppm
moisture; 4000
ppm oil; 330 ppm
non-condensable gases
in air

With hermetic compressor and automatic
oil
return
2 stage
0.07
-0.127 mVmin.
Replaceable with moisture indicator
Selectable charge weight and automatic delivery
Dedicated Refrigerant R134A port connections.
Heating element
to
increase pressure
Condition and range
All figures apply
to a
cold belt.
New belt
578 to 623 N

If tension
is
below
356 N,
reset
at 512 to 534 N

New belt
147 to 153 Hz

If tension
is
below
110 Hz,
reset
at 132 to 138 Hz

Note:
The
tension
is
measured
midway between the
compressor
and crankshaft pulleys. For a new
belt,
rotate engine three
revolutions minimum and then re-check the tension.

May 1996
8-5

Air Conditioning
General Description 5^^?
climate Control System
Features
Refrigerant R134A (Hydro fluorocarbon), non ozone depletory.
PAG (polyalkylene glycol) synthetic compressor lubricating oil.
Dedicated and improved compressor for Refrigerant R134A.
Quick fit and release self sealing charge and discharge ports.
Triple pressure (Trinary) switch to control the compressor (incorporated into the liquid line).
Clamp retained 'O' ring seals at the expansion valve and evaporator.
All aluminium evaporator matrix and pipe work.
Aluminium receiver-dryer (without sight glass) and HFC dedicated desiccant.
Parallel flow extended height condenser.
Single muffler situated in the suction hose.
Improved electrical system connectors.
Improved system control panel.
System Recognition
Identification Features
Aluminium pipes.
Large diameter, quick release charge and recovery ports.
No sight glass.
8-6 May 1996

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

Air Conditioning //—->> "^^Izz^^ • ^ ^
General System Procedures L ^—/ ' —^ ^./^
Adding Refrigerant
In order that the air conditioning system may operate efficiently it must contain a full refrigerant charge. The
indications of some system defects, and the results of certain tests, shows that
a
low charge
is
the most probable cause
of the fault. In such cases the charge shou
Id
be recovered from the
system,
the weight noted, and the correct amount

installed.

Note: Never attempt to
guess the
amount of refrigerant in
a
system.
Always recover and
recharge
with
the
correct
charge
weight,
this is the only
accurate
method.
Caution: If oil is drawn out during the recovery
process,
the correct amount can be added directly from your
recovery-recycle-

recharge station
(if so
equipped)
prior to the charging
process.
It must be
stressed
that the need to protect
compressor
oil from
moisture is vital, observe
the procedures
in Handling Lubricating Oil.
Warning: Liquid refrigerant boils at -29°C (-20°F) at atmospheric pressure. Serious injury, even blindness, can occur if
the refrigerant comes into contact with the eyes.
Goggles and gloves must be warn while working with refrigerant.
First Aid
If refrigerant should contact the eyes or
skin,
bathe 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 eye specialist.
8-14 May 1996

^=2?
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