Subaru Impreza 2003, Service Manual

Page: 2765 / 3610

AC-3
HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS)
GENERAL DESCRIPTION
2. General Description
A: CAUTION
1) Never connect the battery in reverse polarity.
• The Auto A/C control module will be destroyed
instantly.
2) Do not disconnect the battery cables while the
engine is running.
• A large counter electromotive force will be gener-
ated in the alternator, and this voltage may damage
electronic parts such as A/C control module.
3) Before disconnecting the connectors of each
sensor and the A/C control module, be sure to turn
off the ignition switch.
• Otherwise, the Auto A/C control module may be
damaged.
4) Every Auto A/C-related part is a precision part.
Do not drop them.
5) Airbag system wiring harness is routed near the
A/C control panel (A/C control module) and junction
box.
CAUTION:
• All airbag system wiring harness and con-
nectors are colored yellow. Do not use electri-
cal test equipment on these circuits.
• Be careful not to damage the airbag system
wiring harness when servicing the A/C control
panel (A/C control module) and junction box.
B: INSPECTION
Before performing diagnosis, check the following
items which might affect A/C system problems.
1. BATTERY
1) Measure the battery voltage and specific gravity
of electrolyte.
Standard voltage: 12 V
Specific gravity: Above 1.260
2) Check the condition of the fuses for A/C system
power supply and other fuses.
3) Check the condition of the harnesses and har-
ness connectors connection.
2. ASPIRATOR HOSE
1) Turn the ignition switch to ON and push the
A/C switch.
2) Turn the temperature control dial to maximum
hot position.
3) Turn the air flow control dial to “DEF” position.
4) Turn the fan speed control dial to 4th position.
5) Firmly hold a thin paper (b) in front of the in-ve-
hicle sensor suction port (a) for the auto A/C control
unit and check that the paper moves towards the
port indicating that air is being sucked into the port.
NOTE:
Ensure the paper does not get sucked into the port.
6) If the paper does not move at all, remove the
auto A/C control unit <Ref. to AC-30, REMOVAL,
Control Unit.> and check for improper connection
of the aspirator hose (a), auto A/C control unit and
heater unit, and secure as necessary.
3. REFRIGERANT LINE
Check the connection for refrigerant line (A) and
high-pressure pipe.
4. CONTROL LINKAGE
1) Check the state of mode door linkage.
2) Check the state of air mix door linkage.
3) Check the state of intake door linkage.
AC-00648
20
25
30
(b)
(a)
(a)
AC-00649
(A)
AC-00665