Aston Martin DB7 Workshop Manual page 344

^=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 w i l l 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