1997 ASTON MARTIN DB7 relay

o --^ ^^?
Air Conditioning Repair Procedures
Blower Motor High Speed Relay Renewal
6.
7.
8.
Place the flap box assembly to the fan housing and
reconnect the electrical connections.
Fit and tighten the screws securing the flap box to
the housing.
Raise the re-circulation flap, fit and tighten the
remaining screw.
Refit the blower motor assembly.
Reconnect the battery earth-ground
lead.

8.2.11.1
Blower Motor
High Speed
Relay
Renewal

1.
Remove the blower motor assembly complete.
Figure 7.

2.
Open the flap for access.
3. Using a suitable tool remove the relay from the
blower assembly (Fig.
1
-1).

4.
Fit a
new relay
and
refit the blower motor assembly.
May 1996 8-61

Air Conditioning
Portable Diagnostic Unit - Signal Monitoring 3^^?
Air Conditioning Signal Monitoring
The following signals can be monitored using the PDU. The abbreviated name of the signal is shown on the PDU
display.
Display Name Full Signal Name
AMBTEMP Ambient temperature sensor
ARECIP Auto-Recirculation input
ARECOP Auto-Recirculation output
AUX+ Auxiliary battery positive
CLUREL Clutch relay drive output
CVSOL Centre vent solenoid
DEFSOL Defrost solenoid
DIFF Temperature differential
EVSEN Evaporator sensor
FANDEF Fanspeed defrost
FANHIG Fanspeed high
FAN LOW Fanspeed low
FANMED Fanspeed medium
FIVEV Five volt supply voltage
FORSERL Lower servo forward drive
FORSERU Upper servo forward drive
GND10 Ground voltage
GND2 Ground voltage
GND38 Ground voltage
GND45 Ground voltage
GND6 Ground voltage
HSREL High speed relay drive
ICSEN In-Car sensor
LBLOFB Left blower feedback voltage
LBLOWOP Left blower output voltage
LSERFB Lower servo feedback potentiometer
MPROBE Measurement probe
POWIN+ Switched power input
POWOP+ Power output
RBLOFB Right blower feedback voltage
RBLOWOP Right blower output voltage
REF Reference signal
REVSERL Lower servo reverse drive
REVSERU Upper servo reverse drive
TEMPDEM Temperature demand
USERFB Upper servo feedback potentiometer
WATSW Water switch
WATVAL Water valve
8-66 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

Air Conditioning
Portable Diagnostic Unit - Signal Definitions ^27
Defrost Solenoid
(DEFSOL)
Temperature Differential
(DIFF)
Evaporator Sensor
(EVSEN)
Fanspeed Defrost
(FANDEF)
Fanspeed High
(FANHIG)
Fanspeed Low
(FAN LOW)
A/CCM Pin 11 ref Pin 6
The defrost solenoid controls the operation ofthe screen vents. When the solenoid
is energised, the screen vents will be held closed by the vacuum created. To open
the vents the solenoid is de-energised.
The solenoid is energised when a ground supply is provided to pin 11. The
solenoid is de-energised when the ground supply is removed, at which point 10+
volts can be read at pin 11.
A/CCM Pin 28 ref Pin 6
This sets the differential between the position ofthe upper and lower flaps. With
minimum differential selected, pin 28 should read between 0 and 100 millivolts.
The voltage at pin 28 will rise smoothly as the differential is increased, up to a
maximum of 2.885 volts.
A/CCM Pin 5 ref Pin 6
This sensor monitors the temperature of the evaporator matrix, the output is used
to trigger the compressor circuit via the A/CCM pin 20. Operating conditions are
2.732 volts at 0 degrees Celsius ±0.01 volts for every degree Celsius above or
below zero.
A/CCM Pin 27 ref Pin 6
This signal is normal ly held at 3.6 ±0.8 volts by the control module. When Defrost
is selected from the control panel, the line is pulled down to 0.6 volts or below.
This will cause the defrost flaps to open by applying system voltage (approx 11
volts) to pin
11.
In addition, both fans will go to full speed i.e. high speed fan relay
energised .
A/CCM Pin 15 ref Pin 6
This signal is generated from the fan speed control switch.
Switch at High, pin
1
5 should read 0.6 volts.
Switch at Off, L, M or D positions, pin 15 should read 3.6 ±0.8 volts.
A/CCM Pin 13 ref Pin 6
This signal is generated from the fanspeed control switch.
Switch at Low, pin 13 should read 0.6 volts.
Switch at Off, M, H or D positions, pin 13 should read 3.6 ±0.8 volts.
8-68 May 1996

Air Conditioning
Portable Diagnostic Unit - Signal Definitions ^^P
Ground Voltage
(GND2)
Ground Voltage
(GND38)
Ground Voltage
(GND45)
Ground Voltage
(GND6)
High Speed Relay Drive
(HSREL)
In-Car Sensor
(ICSEN)
A/CCMPin2refPin6
A/CCM Pin 38 ref Pin 6
A/CCM Pin 45 ref Pin 6
A/CCM Pin 6 ref Battery -ve
The four ground signals above must be at battery negative voltage at all times.
A/CCM Pin 16 ref Pin 6
The high speed relay drive signal is used to energise the high speed relay and to
run the blowers at full speed, bypassing the normal fan control circuit. The high
speed relay will be energised whenever Defrost or High speed Fans is selected.
Relay energised, pin 16 should read 10+ volts
Relay de-energised, pin 16 should read below 0.5 volts.
If the signal at pin 16 is correct but only one fan responds, suspect a fault in the
harness or relay.
A/CCM Pin 4 ref Pin 6
The in-car temperature sensor operates in the range 0-5 volts. Actual output is
2.732 volts at 0 degrees Celsius ±0.01 volts for every degree Celsius above or
below zero. The sensor signal forms a reference point for the whole system.
If the signal on this pin remains at less than
1
volt, suspect either a short to ground
on the signal wire or an open circuit on the 5 volt supply line to the sensor.
If the signal rises to approximately 3 volts, then suspect an open circuit on the
ground supply to the sensor.
8-70 May 1996

^
The Aston Martin Lagonda Diagnostic System
Users Guide
Signal Description
lACDTCY Idle Air Control Duty Cycle (% open)
lAT Intake Air Temperature - °C or raw input counts
lAT STAT Air Temperature - Temperature sensor failure
lAT-V Intake Air Temperature - Volts or raw counts
IGN Desired Ignition Timing - ° BTDC
INDS Input from manual lever position sensor (counts)
IPWA Injector Pulse Width in mS- Bank A (Cylinders
1
-3)
IPWB Injector Pulse Width in mS- Bank B (Cylinders 4-6)
LAMSE1 Current Short Term Fuel Trim 1, adjustment from stoich - (% of range)
LAMSE2 Current Short Term Fuel Trim 2, adjustment from stoich - (% of range)
LFC Low Speed Fan Status
LOOP Fuel Control -1 = Open Loop, 0 = Closed Loop
MAF MAX Maximum Mass Air Flow signal during normal running
MAF Raw MAF sensor output (A/D counts)
MAF STAT Mass Air Flow Meter - MAF sensor failure
MIL Mali Indicator Lamp Status -1 = Lamp On
Mis HI Cumulative misfires detected by misfire test (Hi bit).
Mis LO Cumulative misfires detected by misfire test (Lo bit).
Mis nc HI Cumulative misfires detected by a misfire test (Hi bit).
Mis nc LO Cumulative misfires detected by a misfire test.
Misi HI Cumulative misfires detected by cylinder
1
misfire test (Hi bit).
Misi LO Cumulative misfires detected by cylinder
1
misfire test (Lo bit).
Mis2 HI Cumulative misfires detected by cylinder 2 misfire test (Hi bit).
Mis2 LO Cumulative misfires detected by cylinder 2 misfire test (Lo bit).
Mis3 HI Cumulative misfires detected by cylinder 3 misfire test (Hi bit).
Mis3 LO Cumulative misfires detected by cylinder 3 misfire test (Lo bit).
Mis4 HI Cumulative misfires detected by cylinder 4 misfire test (Hi bit).
Mis4 LO Cumulative misfires detected by cylinder 4 misfire test (Lo bit).
Mis5 HI Cumulative misfires detected by cylinder 5 misfire test (Hi bit).
Mis5 LO Cumulative misfires detected by cylinder 5 misfire test (Lo bit).
Mis6 HI Cumulative misfires detected by cylinder 6 misfire test (Hi bit).
Mis6 LO Cumulative misfires detected by cylinder 6 misfire test (Lo bit).
MISF Misfire Monitor - 1 = Currently misfiring
ODCODES Total number of on-demand codes currently stored.
PGM CVS DC Purge Management Duty Cycle (% on)
PIP Profile ignition Pick-Up - PIP input level
PNP Park Neutral Position Switch
R-BIAS1 Rear bias trim (Bank 1, cylinders
1
-3)
R-BIAS2 Rear bias trim (Bank 2, cylinders 4-6)
RATCH Lowest TP reading during driving
TP MAX Maximum Throttle Potentiometer signal during normal running
TP STAT Throttle Position Sensor - TP sensor failure
TP Throttle Potentiometer - Volts or counts
TPR-V Raw counts from sensor
TQ-NET Net torque into the torque convertor
TRIP OBDII Drive Cycle Complete (except cat monitor) - 1 = Trip completed
TRIPCNT Number of Completed OBDII Trips
VS MAX Maximum Vehicle Speed signal during normal running
VS STAT Vehicle Speed Sensor mode flag
VS Vehicle Speed - MPH
WAC Wide Open Throttle A/C Cut-Off -1 = High (WOT Relay)
September 1996 9-37

The Aston Martin Lagonda Diagnostic System
Users Guide
•=2?

Clear all Trouble Codes
Selecting the clear all trouble codes icon will invoke a
confirmation window.
EEC-V EMS
dri
dri
CONFIRM
Clear all logged trouble
codes?
O

'Clear
All Codes' confirmation
screen

Selectingthe'tick'will instructthePDU to clear all logged
trouble codes in the selected module
and
return to the no
logged codes screen.
Select the 'tick' icon to exit Diagnostic Trouble Codes.
Clear Selected Trouble Codes
(95 MY Zytek Engine Management Only))
If
you
wish only to clear selected codes on the Zytek ECU
and
leave others
for later
investigation,
proceed
as
follows:
Highlight only the trouble code(s) to be cleared.
ZYTEK EMS
1 : Idle speed control valve driver #1
5 : Purge Valve driver #1
12 : Cooling fan#l relay driver
14 : Lannda heater
#2
driver
1 : Idle speed control valve driver #1
Highlighting
Selected
Trouble
Codes

Select the 'clear selected trouble codes'
icon;
this will
invoke a confirmation window.
Selectingthe 'tick' icon will instruct
the
PDU to clear only
the selected trouble codes from the control module fault

table,
and if successful, the system will return to the
'Diagnostic trouble codes' screen.
If any attempt to clear trouble codes is unsuccessful, a
warning window will be displayed.
This will indicatethat
some selected
trouble codes remain
logged,selectingthe'tick'iconwillreturntothe'Diagnostic
trouble codes' screen.
Select the 'tick' icon again to exit Diagnostic Trouble
Codes.
9-54 September 1996