Subaru R-12, R-134A User Manual
ver the years, Subaru air conditioning systems have taken many different
shapes and sizes, from full manual, cable and vacuum-controlled systems like
those found on Loyale models, to the fully automatic electronically controlled
systems employed by the SVX and some Legacy models. Because of this great
diversity in Subaru air conditioning systems, it would be impossible to tell you
everything there is to know about every single Subaru air conditioning system in
this edition of The End Wrench.
What we will do instead is to give you a cross-section summary of recent
Subaru air conditioning systems. We’ll show you what’s unique and different
about each system, and describe the best troubleshooting and repair strategies
for these systems.
In compliance with government requirements, all Subaru vehicles manufactured
within the past few years are equipped with R-134a air conditioning systems.
But there are still a large percentage of Subaru vehicles on the road with R-12
refrigerant in their A/C sytems. We’ll explain how to safely handle R-12 and
R-134a refrigerants, and we’ll also explain your repair and retrofit options
when a Subaru equipped with an R-12 air conditioning system comes to your
shop for repairs.
Subaru Air Conditioning Systems
Introduction
End Wrench
The
O
4
Systems
Air Flow System
The purpose of the air flow system is to provide
air to the heating, ventilation, defroster, and air
conditioning systems.
Control of the air flow is accomplished by four
types of systems which are Subaru model specific:
➊ Manual cable - Justy
➋ Manual cable/vacuum -Loyale
➌ Manual cable/electric - Legacy,
Impreza, and XT
➍ Automatic electric - SVX
The mode selector controls the routing of air to the defroster, heater core, air
conditioning evaporator, and the outlet ducts. The temperature control
lever adjusts the temperature of the air admitted to the passenger compartment and regulates the flow of air through the heater core via the air mix
doors. The fan switch controls the speed of the fan and thus the
volume of air that flows through the evaporator and heater cores.
Loyale vehicles have vent control levers which are not a part of the mode
selector switch. These are manually adjusted by the driver and passenger to
admit or restrict the flow of outside air through side vent outlets.
The Legacy and the Impreza have eight position mode panels while the
Loyale and XT have six button panels. The additional VENT mode supplies
outside air to the passenger compartment through the dash vents. The flow
of vent air may be increased by using the fan, and heated by increasing the
temperature control setting. The DEF/HEAT mode switches the A/C compressor ON and supplies air flow to the defrost and floor outlets. The remaining
mode switches operate similar to other Subaru A/C system controls.
The air flow unit used on Legacy vehicles equipped with manual A/C
systems is similar to the unit used on Automatic Climate Control
equipped vehicles.
Loyale Vacuum System (Mode Control)
Only Loyale vehicles use a manually actuated vacuum operated system to
control the position of the mode and circulation shutter actuators.
The vacuum system operates the air flow shutters in all Loyale vehicles. Check
vacuum to the shutter actuators if the defroster, floor vents, or fresh air vents do
not operate properly. The vacuum system also provides vacuum to the FICD
diaphragm based upon FICD solenoid signal, if so equipped.
XT Mode Control System
In XT vehicles, the electrical mode control system operates the various mode
shutters and doors.
Electric motors control the operation of the air flow shutters in the XT. The
motors operate the shutter actuators through a gear drive and linkage assembly.
If the flow of air through the defroster, floor vents, or other vents is insufficient,
check operation of the shutter actuators and switches.
A/C Cut System
This system is installed on many 1987 and later model year automatic transaxle
equipped Subaru vehicles. The purpose of the A/C cut system is to improve
engine performance during full throttle acceleration. Refer to the chart to
determine component application for the various models listed.
Note: All sequential MFI equipped vehicles feature
A/C cut systems.
Components
Fuel
Model System Trans A/C A/C
Cut K/D K/D Cut
Unit SW. Relay Relay ECM TPS Map
XT / XT6 / ”L” MFI 4EAT
”L” MFI 3AT
TBI
Legacy SVX MFI ALL
Justy Impreza
Justy Carb ECVT
”L” / HB Carb 3AT
“L” Series Air Flow System Controls
Vent Switches
Legacy/Impreza Mode Panel
Electrical System Operation
A/C Cut System
5
Fast Idle Control Device (A/C Idle Air Control)
On manual transaxle equipped Justy vehicles, the FICD is incorporated in the
idle-up system. Proper adjustment and operation is outlined in Service Bulletins
02-70-89 and 02-72-89.
On ECVT equipped carbureted vehicles an air/fuel bypass control system
performs the FICD function. The ECVT air bypass control system consists of
an air bypass valve, an adjusting screw, and an air bypass solenoid. The system is
designed to increase idle speed whenever the A/C relay is activated by supplying
additional air/fuel into the intake manifold.
Bypass air enters through the air horn on the secondary side.
The airflow is regulated by an adjusting screw. When the bypass valve opens,
bypass air/fuel enters the manifold below the secondary throttle plate.
When the adjusting screw is turned clockwise, bypass air/fuel is reduced and
the idle speed is lowered. When the adjusting screw is turned counter clockwise,
bypass air/fuel is increased and the idle speed is increased.
Note: Always refer to the appropriate Justy model year Subaru Service Manual
sections 2-2 and 2-6 for the proper ECVT FICD adjustment procedures
and specifications.
TBI system equipped Loyale vehicles control the FICD function through the
ECM, the idle air control valve (IAC), and the A/C switch. The air conditioning
ON/OFF switch is an input to the ECM. The ECM operates the idle air control
valve (IAC) to adjust the idle speed to compensate for the increased compressor
load. No adjustment is required.
On all model year Loyale and XT MFI vehicles, an FICD solenoid incorporated
in the throttle body provides the increase in idle speed. The throttle body includes
an adjustment screw for adjusting the FICD specification.
All Legacy, SVX and XT6 vehicles use an idle air control valve to provide the
FICD function. The valve opens a port during A/C operation which admits
additional air into the induction system.
Impreza vehicles use a solenoid which initially compensates for the increased
compressor load when the air conditioning system is switched ON. The A/C IAC
then compensates to maintain engine speed at target RPM.
Note: The Impreza FICD solenoid is set at the factory and should not require
adjustment. Any changes to the adjustment can affect driveability and vehicle
emissions during cold engine operation.
Justy MFI vehicles increase idle speed by admitting additional air into the air
collector assembly through the FICD solenoid which is opened by a signal from
the MFI control unit.
The
6
End Wrench
Subaru Air Conditioning Systems
Bypass Adjusting Screw
(ECVT)
TBI (IAC)
MFI/TBI FICD Operation
A/C Idle Air Systems Impreza FICD
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