Aston Martin DB7 Workshop Manual page 346

3^7? Air Conditioning
Portable Diagnostic Unit - Signal Definitions
Fanspeed M e d i u m
(FANMED)
Five Volt Supply
(FIVEV)
Flap Servo Drive Signals
Lower Servo Forward Drive
(FORSERL)
Upper Servo Forward Drive
(FORSERU)
Lower Servo Reverse Drive
(REVSERL)
Upper Servo Reverse Drive
(REVSERU)
Ground Voltage
(GND10)
A/CCMPin 14ref P i n 6
This signal is generated from the fanspeed control switch.
Switch at Low, pin 14 should read 0.6 volts.
Switch at Off, L, H or D positions, pin 14 should read 3.6 ±0.8 volts.
A/CCM Pin 43 ref Pin 6
This 5 volt rail provides the power supply for all the sensors and the feedback
potentiometers. Any variation in this signal would totally upset the balance of the
whole system.
The servo drive signals control the position of the upper and lower flaps. The drive
signals work in pairs, two for the upper and two for the lower flaps.
A/CCM Pin 37 ref Pin 6
A/CCM Pin 40 ref Pin 6
A/CCM Pin 41 ref Pin 6
A/CCM Pin 42 ref Pin 6
When the flaps are stationary, all signals will be at 0.6 volts approximately. When
the flap(s) is being driven, the drive iine(s) will rise to approximately 6 volts.
As the flap approaches its final position, the drive signal w i l l be pulsed to nudge
the flap to the exact position required.
Note: If a drive signal rises to above 8.5 volts and the servo motor does not operate, suspect
an open circuit within the servo.
A/CCM Pin 10 ref Pin 6
This is the ground supply from the A/CCM to the in-car sensor and should read
below 10 millivolts.
Failure of this line will cause the in-car sensor to believe the vehicle temperature
to be at maximum all the time, thus forcing the system into permanent cooling.
Under these circumstances, pin 4 (in-car sensor output) will be approximately 5
volts.
May 1996
8-69