checking oil ASTON MARTIN DB7 1997 Workshop Manual

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

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
System Checking with the Manifold Gauge Set D'^?
Purging the Test Hoses

1.
With the manifold test set attached to the system.

2.
Purge the high pressure test hose by cracking open
the high pressure side hand valve on the manifold
gauge set for 3 to 5 seconds. This allows the system
refrigerant to purge the air from the test hose and
discharge through the manifold centre test hose.
Immediately cl ose the high pressure side hand

valve.

3. Purge the low pressure test hose in the same manner
by cracking open the low pressure side hand valve
manifold gauge
set
for 3 to 5 seconds, then close the
hand valve.
Stabilising the System
The manifold gauge set is now attached to the
system and the test hoses purged of air. With both
hand valves closed, the system must be operated
for a few minutes to stabilise all pressures and
temperatures throughout the system in order to
obtain accurate test gauge readings.
Proceed as follows:

1.
Place all test hoses, gauge set and other equipment
away from all engine moving parts. Also keep the
hoses from touching the hot engine manifold.

2.
Start the engine and adjust engine speed to fast idle
3. Turn on the air conditioning and set for maximum
cooling with blower fans on high speed

4.
Open the car doors and/or windows (to quickly
eliminate car interior heat).
5. Operate the system under these conditions for 5 to
10 minutes to stabilise the system ready for testing.
6. Check the system for full refrigerant by noting the
sightglass indications. Some refrigerant loss occurs
over a period of time.
Note: The air conditioning
system
must contain a full
refrigerant
charge
before an accurate
system
check can
be
made.
An insufficient
charge
is indicated by
a stream

of
bubbles
or
foam.
If
the
refrigerant charge is low, the

system
must
be
fullydischarged into
a
refrigerant recovery
station and recharged with the correct weight of refrigerant
82.30.08. Do not top up a
system
with refrigerant.
Leak Test
A high proportion of ail air conditioning work
consists of locating and repairing leaks.
Many leaks are located at connections and are
caused by vibration. They may only require the re-
tightening of a connection or clamp.
Occasionally a hose rubs on a structural part of the
vehicle and creates a leak, or a hose deteriorates
which will require a replacement.
The specified maximum leakage rate at each fitting
is 0.5 kg of R 134a in 40 years and a leak detector
capable of operating to this accuracy must be

provided.
To check place the leak detector probe at
the lowest pointofeach joint, pausefortwo seconds.
Do not wave the probe about as refrigerant is
heavier than air and flows to the lowest point. If a
leak is greater than 0-5 kg in forty years is detected
identify the leak point for rectification.
Check that the leaking fitting has been tightened to
the correct torque. If the torque is low, rectify and
repeat leak test. If the torque is satisfactory,
depressurise the system, dismantle the leaking
connection and check the quality of the fitting.
If the fitting is satisfactory, clean and reassemble
after applying a thin film of refrigerant to the seat of
aflarefitting, ora newoiled "O" ring to an "O" ring

fitting.

Tighten to the correct torque.
Charge the system with 200 g of El 34A and leak test
the rectified system. If the system is satisfactory,
depressurise, evacuate and recharge the system.
If the system is unsatisfactory, i.e. leakage greater
than 0.5 kg in forty years, depressurise and replace
the leaking assembly.
8-40 May 1996

=2?
Air Conditioning
System Checking with the Manifold Gauge Set
Pressure Temperature Relationship.
Note:
Pressures
shown are under exact conditions
(see
test
conditions) and
are
not
necessary
true for every
car

checked.
Ambient Temperature is given as the air
surrounding the
condenser
and
is
taken 5 cm in front of
the
condenser.

Test Conditions.
Use a large fan to substitute for normal ram air through the
condenser. Engine adjusted to fast idle speed.
All conditions equivalent to 30 m.p.h. or 48 km/h.
Ambient
Evaporator
Temp °C
16
18
21
24
27
29
32
35
38
41
43
46
49
High
Pressure
Gauge
Reading
Ibf/in2
95-115
105-125
115-125
130-150

1
50-170
165-185
175-195
185-205
210-230
230-250
250-270
265-285
280-310
Low
Pressure
Gauge
Reading
Ibf/in2
10
12
4
16
18
20
22
24
26
28
30
35
40
45
50
55
60
65
70
Ten
-16
-14
-12
-10
-8
-6
-5
-4
-3
-1
0
2
5
9
11
14
17
19
21
Normal operating ambient temperature range is:
-24 to 43°C.
Normal operating evaporator temperature range
is:-12toO°C.
Under normal running conditions system pressure
should be, as follows:
Lowside:1.05to2.10kgf/cm21.034to2.06bar15
to 30 ibf/in2
High side: 13.00 to 14.40 kgf/cm2 12.75 to 14.34
bar185to205lbf/in2
Manifold Gauge Set Check Procedures
Refrigerant Slightly Low.
Complaint.
Little or no cooling.

1.

2.

3.

4.

1.

2.

3.

4.

5.
6.
7.
BLUE LOW SIDE
KED
HIGH SIDE
Condition.
The low side gauge reading is too low.
The high side gauge reading is too low.
A stream of bubbles evident in the sight glass.
The discharge air from the evaporator only
slightly
cool.

Diagnosis.
The system low on refrigerant due to slight leak.
Correction.
Test the system for leaks.
Depressurise the system.
Repair the leaks, and if necessary renew hoses or

units.

Check the compressor oil level. The system may
have lost oil due to leakage.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
Operate the system and check the performance.
May 1996 8-41

Air Conditioning
System Checking with the Manifold Gauge Set [n::S3^^?
Refrigerant Excessively Low.
Complaint.
Cooling is not adequate.
Air In The System.
Complaint.
Cooling is not adequate.
BLU£ LOW SIDE SlUE LOW SIDE MD HIGH SIDE
5.
6.
7.

Condition.

1.
The low side gauge is reading very low.

2.
The high side gauge reading very low.
3. No bubbles or liquid evident in the sight glass.

4.
The discharge air from the evaporator is warm.
Diagnosis.
System refrigerant excessively low. Serious leak

indicated.

Correction.

1.
Test the system for leaks.
Note: Partially recharge the
system
before testing the

system
for
leaks
to
ensure that leak detection is
obtained.
Depressurise the system.
Repair the leaks, and if necessary renew hoses or

units.

Check the compressor oil level. The system may
have lost oil due to leakage.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
performance.

2.

3.

5.
6.
7.
8-42
Condition.
The low side gauge reading
is
constant and does not

drop.
The pressure should drop until the compressor
cycles (thermostat control)
The high side gauge reading is slightly high (or
slightly lower especially if a large fan is used to
substitute ram air).
The sight glass is free of bubbles or only shows an
occasional bubble.
Thedischarge air from theevaporator
is
only slightly

cool.

Diagnosis.
Non condensables present in the system. Air or
moisturepresent instead of afullrefrigerantcharge.
Correction.
Test the system for leaks. Test the compressor seal
area very carefully.
Depressurise the system. Repair the leaks, and if
necessary renew hoses or units.
Renew the drier bottle, probably water saturated .
Check the compressor oil level.
Evacuate the system using a vacuum pump.
Recharge the system with new refrigerant.
Operate the system and check the performance.
May 1996

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