Input-Output Voltage Signals - Aston Martin DB7 Workshop Manual

Air Conditioning
Electronic Control Module
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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