ASTON MARTIN DB7 1997 Workshop Manual
Manufacturer: ASTON MARTIN, Model Year: 1997, Model line: DB7, Model: ASTON MARTIN DB7 1997Pages: 421, PDF Size: 9.31 MB
Page 291 of 421
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
Page 292 of 421
Air Conditioning
Functional Check
Functional Check
This functional check procedure is provided as a simple system validation and is structured to augment the Portable
Diagnostic Unit (PDU).
Stage 1 (Cold engine only, if not proceed to Stage 2)
Procedure Normal System Reaction
1.
Ignition ON
Select MIN temperature, MAN, speed 3, Mid face.
(Engine Stationary) Fans Start
2.
Select MAX temperature Fans continue to run
3. Ignition OFF
Select MAX temperature and defrost
Ignition ON Fans start at maximum speed
4.
Select fan speed
1
Fan speed adjusts accordingly - system OK
Stage 2
Procedure Normal System Reaction
1.
Start up engine and warm up
Select fan speed 1, MAN, MAX TEMPERATURE
and mid face
2.
Open all vents Fans start after 3 seconds
2.
Select fan speed 2 Fan speed increases then stabilises
3. Select fan speed 3 Fan speed increases then stabilises
4.
Select defrost Fan speed steady at high
All air at screen and dash end
5. Re-select fan speed 1
Select AUX ignition key position
6. Slowly select MIN temperature Solenoids switch 1. centre vent
2.
water valve
3. Re-circulation
7. Re-select MID temperature
8. Select DEM Solenoid clicks
Air at screen
9. Select manual re-circulation Solenoid click
10.
Check flap for position
11.
Run Engine to normal temperature
12.
Select: MAN, 3/4 MAX heat and fan speed 2 Air from door vents
cool,
air temp from foot outlet slightly warm
13.
Select MAX temperature and air differential to hot face All vent outlets max temp except screen vent
14.
Select temperature
approx. 1/4 MAX heat and mid face level Cool air from centre vents
15.
Select MIN temperature Blower flaps at re-circulation position
All outlets blowing cold air except screen vent
May 1996 8-15
Page 293 of 421
Air Conditioning //—^ ^ci^^ • ^ ^
Fnnrtlnn;il fhprk I *-/ -^ r <
Procedure Normal System Reaction
16.
Select ECO Blower flaps revert to fresh air position
17.
Select AC Engine revs change then stabilise
18.
Select fan speed 3 Small increase in fan speed
19.
Select fan speed 2 Fan speed lower
Centre vent and dash end cold
footwell cool
20.
Select MAX temperature
allow in-car temperature to stabilise Hot air from footwell,
(Passenger side underscuttle panel must be in place) warm from dash end
21.
Select MIN temperature and mid face level System goes to full cooling automatically
Cold air from all vent except from screen vent
Centre vent open
Blower at re-circulation
22.
Select DEMIST and full heat Demist vents open, centre vent closes and
blower flaps revert to fresh air position
System check now complete System good.
Note: A small amount of air will bleed from the
ends
of the
demist-defrost vents
in all
cases,
but there should be no leak along
the length of the vents.
8-16 May 1996
Page 294 of 421
^=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
Page 295 of 421
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
Page 296 of 421
^2?
Air Conditioning
Electronic Control Module
Electronic Control Module (ECM)
The Electronic Control Module (ECM) is located on the right hand side of the heater unit.
The ECM has a digital microprocessor that allows the air conditioning system to maintain the selected in-car
conditions. To do this it compares the signals from the in-car controls with those it receives from the system
temperature sensors and feedback
devices.
On the basis of these comparisons it makes appropriate voltage changes
to vary the blower motor
speed,
flap position and the state of other solenoids that effect the selected temperature
demand.
The ECM is a non-serviceable component but may be interrogated for system
testing.
Care must be exercised when
connecting
the test
equipment
as the ECM
may
be
irreparably
damaged
should any ofthe
test
pins
be
shorted or bent.
20 21 22 23
Q
A / A \/
Em
10 11
1.
Electronic control module (ECM)
2.
Differential temperature control
3. Temperature control
4.
Fan speed control
5. Ambient temperature sensor
6. Motorised in-car aspirator
7. Evaporator temperature sensor
8. Coolant temperature switch
9. Lower flap feedback potentiometer
10.
Upper flap feed back potentiometer
11.
Left hand blower motor feedback
12.
Right hand blower motor feedback
13.
High speed relay
14.
High speed relay
15.
Compressor clutch
16.
Blower motor
17.
Blower motor
18.
Lower flap servo motor
19.
LIpper flap servo motor
20.
Defrost vacuum solenoid
21.
Auto re-circulation vacuum solenoid
22.
Centre vent vacuum solenoid
23.
Water valve vacuum solenoid
24.
Air conditioning function switch
May 1996 8-19
Page 297 of 421
Air Conditioning
Electronic Control Module r^^?
Description
The ECM (Fig 1) controls the air conditioning
system so that selected temperaturesare maintained.
It cannot be repaired but input and output signals
can be measured, using the PDU, for diagnostic
purposes.
Input-Output Voltage Signals
The following voltage signal levels are input and
output from the ECM:
Digital input levels:
Low
High
Analogue input levels:
General
Blend Flap Potentiometer
Digital output levels
Relays On
Off
Vacuum manifold Pull-in
Drop-out
Analogue output levels
Blend Flap Servo Motors
Blower Motors
0.16 to 1.1V
3.70 to 4.50V
0 to 0.2885 V
0 to 5.0V
8.0V
1.0 to 5.0V
5.6V (typical)
3.5V (typical)
0.5 to 6.5V
0.5 to 2.5V
figure 1.
The ECM
is
turned on when the ignition
is
turned on
to auxiliary position 1. its operating range is 13.5-
14.2 volts.
The ECM power unit supplies +5 volts for the
temperature sensors, feedback potentiometers and
high speed relays.
An integrated circuit protects the ECM against
reversed polarity and voltage surges.
Caution: Take care when connecting test equipment. If
test pins are allowed to be shorted together, to
ground or to positive supplies the ECM will be
damaged.
8-20 May 1996
Page 298 of 421
^n:m^^^
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
Page 299 of 421
Air Conditioning
In Car Controls '^^
Air Conditioning Function Switch
The air conditioning function switch (Fig. 4) has
five positions: Economy (ECO), Air conditioning
(AC),
Manual (MAN), Re-circulation and Demist
(DEM). These settings have thefol lowing functions:
ECO (Economy) Inthissettingtheairconditioning
compressor is switched off. No cooling is
available but incoming air may be heated to
the selected temperature. This mode puts a
minimum load on the engine. Pin 23 at the
ECM is earthed through the switch to select
economy mode.
AC This setting allows the heating and cooling
functions to be performed automatically,
the required in-cartemperature
is
maintained
and the air is dehumidified. Pin 26 at the
ECM is earthed through the switch to select
this mode.
MAN (Manual) In the Manual mode the fan speed
and temperature control can be set at any
level and heating or cooling will be
performed despite the internal temperature
of the car. Pins 26 and 19 at the ECM are
earthed through the switch to select this
mode
V (Re-circulation) With this setting selected
the external air inlets are closed and
conditions are maintained by circulating
the air within the car. Heating and cooling
functions are controlled automatically to
give the required in-cartemperature. Pins 9
and 26 at the ECM are earthed through the
switch to select the manual Re-circulation.
DEM (Demist) Air is directed directly onto the
screen in this mode. Air speed and
temperature depend on the selected fan
screen and in-cartemperature. Heating and
cooling functions are still controlled
automatically to give the required in-car
temperature. Pin 8 and 26 at the ECM are
earthed through the switch to give the
required in-car temperature.
B
liD^
-• 1
-• 2
-• 3
-• 4
-• 5
,'^
1 -• 6
-• 7
-• 8
Figure 4.
Key to Fig. 4
1.
AC signal Pin 26 ECM
2.
MAN signal Pin 19 ECM
3. REC signal Pin 9 ECM
4.
DEM signal Pin 8 ECM
5. Earth-ground Pin 1 ECM
6. Earth-ground Pin 1 ECM
7. AC signal Pin 26 ECM
8. ECO signal Pin 23 ECM
A ECO
B AC
C MAN
D Re-circulation
E DEM
8-22 May 1996
Page 300 of 421
'^^p
Air Conditioning
In Car Controls
Fan Speed Control Switch (Mode Switch)
SC On Mode
The system is not operational, a residual
signal to the ECM ensures that the blower
flaps are closed to prevent air entering the
system.
1.
Low Blower Mode
The fan speed is lowandtheairconditioning
function switch is fully operational. Pin 13
on the ECM is earthed through the switch
and a 12V signal is returned to Pin 44.
2.
Medium Blower Mode
The fan runs at medium speed and the
function switch is fully operational. Pin 14
of the ECM is earthed through the switch
and a 12V signal is returned to Pin 44.
3. High Blower Mode
The fan speed is high and the function
switch is fully operational. Pin 15 at the
ECM is earthed through the switch and a
12V signal is returned to Pin 44.
DEF Defrost Blower Mode
The fan speed is
high,
the function switch
and temperature switch are not operational,
front screen vents are fully open and lower
flaps are fully closed. Pin 27 at the ECM is
earthed through the switch and a 12V signal
is returned to Pin 44.
Temperature Sensors
The system has three temperature sensors:
• the ambient sensor (Fig. 5)
the evaporator sensor (Fig. 6)
Figure 5.
Figure 6.
• and the in-car aspirated sensor.
Each sensor containsa semiconductor whose output
or sensing voltage varies with temperature changes.
All three are supplied via pin 43 of the ECM. The
sensing voltages are fed back into the module via
the following pins (Fig. 7):
• ambient temperature sensor - pin 34
• in-car aspirated sensor - pin 4
• evaporator temperature sensor - pin 5
At 0°C the sensing voltage should be 2.732 volts.
This voltage rises or falls by 0.01 volts for every 1°C
change in temperature; for instance, if the
temperature rises 5°C above zero, the voltage rises
by 0.05 volts to 2.782 volts. Sensors have built in
potentiometers which are preset at the factory and
must not be adjusted.
H
Figure 7.
Key to Fig. 7
1.
Sensor
2.
Pin 43 control module
3. Sensing voltages:
Pin 4 In-car aspirated temp sensor
Pin 5 Evap temp sensor
Pin 34 Ambient temp sensor
4.
Earth-ground
May 1996 8-23