Aston Martin DB7 Workshop Manual page 348

Air Conditioning
Portable Diagnostic Unit - Signal Definitions
Left Blower Feedback Voltage
(LBLOFB)
Left Blower Output Voltage
(LBLOWOP)
pin 22 = 5±1 volt
p i n 2 2 = 9 ± l v o l t
pin 22 = 5±1 volt
pin 22 = 2±1 volt
p i n 2 2 = 6±1volt
pin 22 = 2±1 volt
A/CCM Pin 22 ref Pin 6
This signal informs the control module of the present voltage applied to the left
blower. The control module can then monitor and vary this voltage to change
blower motor speed. With Manual selected, the blower operates in four basic
ranges:
Low Speed
Temp M i n :
Temp Med:
Temp Max:
Medium Speed
Temp Min:
Temp Med:
Temp Max:
High Speed
Pin 22 = 1±1 volt at all temperature settings
Defrost
Pin 22 = 1±1 volt at all temperature settings
A/CCM Pin 31 ref Pin 6
This signal is produced by the control moduleto drive the blower motor. The signal
can vary from 0-3 volts depending on blower motor speed. The higher the voltage,
the higher the blower motor speed. This signal is amplified by a simple amplifier
circuit inside the blower motor. This circuit also supplies the feedback signals to
pins 22 and 33.
Note: If the signal rises above 5 volts, then suspect a fault in the amplifier circuit.
Lower Servo Feedback Potentiometer
(LSERFB) A/CCM Pin 29 ref Pin 6
This feedback signal informs the control module of the exact position of the flaps,
enabling accurate control of flap position.
Defrost - Lower flap signal should be 2.9 volts (flap closed) upper flap signal
should read 1.9 volts.
Max Temp - Lower flap signal should read 1.14 volts, upper flap signal should
read 1.9 volts.
Min Temp- Both lower and upper flap signals should read 1 3 0 ± 80 millivolts.
Note: If the feedback sticks low, with the fan continually running, suspect an open circuit
in the 5 volts supply to the feedback potentiometer or the potentiometer itself.
May 1996
8-71