Hyundai Sonata 1991 Shop Manual page 248

MPI SYSTEM
Air Conditioner Relay Control
Y310H3A
When the air conditioner switch is turned on while the engine is at idle, the ISC servo operates to increase the
engine speed. However, there is some delay before the engine speed actually increases. To maintain the engine
free from the air conditioner load during that delay period, the ECU keeps the power transistor off for a fixed time
(about 0.5 seconds) to open the air conditioner power relay circuit. As a result, even if the air conditioner switch
is on, the air compressor is not driven instantly, preventing engine speed drop due to compressor load.
In addition, for automatic-transmission-equipped models, during acceleration when the throttle valve opening is great
(approximately 65
0
or more), the air conditioner power relay circuit is cut off for a fixed time (about five seconds)
for good acceleration performance.
Air conditioner switch
nsor
YI
Air conditioner relay
Air conditioner
compressor
-=-Battery
I ./": I
I I
Air conditioner
switch
,
Crank angle se
~
Throttle position
0
sensor (A/T onl
ECU
(
(
01 ~~
Inhibitor switch
~
IAIT only)
•
~-~
~
~'L
--'-
0';'
AIT : Vehicles with an automatic transaxle
31Y013
31-23