Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 127

OTHER CONTROL SYSTEMS - Air Conditioner Control System
0
AIR CONDITIONER CONTROL SYSTE M
1 . CUT-OFF CONTROL
2 . MAGNETIC CLUTCH RELAY
CONTRO L
The Engine ECU sends a signal (ACT) to the air
conditioner amplifier to disengage the air
conditioner compressor magnetic clutch in order
to stop operation of the air conditioning at
certain engine speeds, intake manifold pressures
(or intake air volumes), vehicle speeds and
throttle valve opening angles .
The air conditioner is turned off during quick
acceleration from low engine speeds (depending
on the vehicle speed, throttle valve position, and
intake manifold pressure or intake air volume) .
This helps maintain good acceleration
performance .
The air conditioner is also turned off when the
engine is idling at speed below a predetermined
rpm . This prevents the engine from stalling .
In some engine models, magnetic clutch
operation is also delayed for a predetermined
length of time after the air conditioner switch is
turned on . During this time, the Engine ECU
opens the ISC valve to offset the drop in the
engine speed due to the operation of the air
conditioner compressor . This prevents the idle
speed from dropping .
This latter control function is called the "air
conditioner compressor delay control" .
+B
This air conditioner control function differs from
the previously-mentioned type in that the
Engine ECU controls the magnetic clutch relay
directly .
When the Engine ECU detects the air conditioner
(A/C) signal from the air conditioner control
assembly, but does not detect the requisite air
conditioner cut-off conditions from various
sensors (see cut-off control to the left), this ECU
outputs a magnetic clutch (ACMG) signal to the
magnetic clutch relay, turning it on . As a result,
the magnetic clutch goes on and the air
conditioner compressor operates .
This air conditioner control function is also
provided with an air compressor delay control .
The operation of this is the same as that in th e
air conditioner cut-off control function .
+B
OHP 8 0
OHP 80
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