Subaru XT 1988 Service Manual page 1026

4-7
AIR CONDITIONING SYSTEM
F.I.C.D.
F.I.C.D. is of the solenoid valve type incorporated into throttle
body. It operates when the air conditioner switch is turned
on. Idle speed need not be adjusted.
Idle speed with F.I.C.D. in operation:
850
±
50
rpm
BE L T PROTECTION SYSTEM
General
Whenever the compressor rpm drops below the specified value,
the belt protection system quickly turns off the magnet clutch
of compressor and operations of alternator, water pump and
power steering oil pump are kept normal. Disengagement of
the clutch causes the compressor pulley to rotate freely so that
belt is not broken.
Operation
In the system as shown in figure, while compressor is operat-
ing, the ratio of compressor rpm to engine rpm is monitored
by a pulser amplifier. When compressor rpm drops more than
20 to 25% below the normal rpm, the system judges as if
compressor is "locked" and turns off the magnet clutch of
compressor.
Once the system defects a "Iocked" compressor, the magnet
clutch remains off until the air conditioner switch is turned
off and turned on again.
MPFI
co ntro I
----+.
Ignition coil unit
(to detect
engine rpm)
MT
Battery
Ignition
switch
Micro switch
Triple
switch
A/C max. unit
-
A/C cut unit (AT only)
Blower switch
L4-1252
Fig.
2
4
x 1,000 rpm
E
e-
5
'"
'"
Q)
9-
..:
0
()
7
6
5
4
3
2
Normal rpm
2 3 4 5 6 7
x 1,000 rpm
Engine rpm
Fig.3 Characteristic curves of "lock" detection
A26·138