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HVAC
15
The moving scroll rolls and slides in small circular
movement with a small friction loss, ensuring smooth
operation even during start-up.
COMPRESSOR RELAY
Compressor relay is located in the MDU (
Main distri-
bution Unit)
located in the engine compartment
which is used to operate the compressor magnetic
clutch. The magnetic clutch continues to operate as
long as air conditioner is under operation. Once the
air conditioner is put in OFF condition, the compres-
sor relay gets cut off and the magnetic clutch gets
disengaged from the compressor. The cut - in and
cut - off of relay is governed by the ENGINE ECU.
The HVAC control unit controls the compressor
ON/OFF indirectly by sending ON/OFF request to
the EMS ECU.
MAGNETIC CLUTCH
SPECIFICATION
NOMINAL VOLTAGE
12V DC
POWER CONSUMP-
TION
35W
BELT TYPE
V – RIBBED BELT (5
PK)
AIR GAP
0.25 TO 0.50 mm
DIRECTION OF
ROTATION
CLOCKWISE
WEIGHT
1.5 Kg
WITHSTAND
VOLTAGE
AC 500V X 1Min
PULLEY DIAMETER
Ø110
Magnetic clutch is used to connect and disconnect
the compressor from the engine.
Main components are stator, rotor, and pressure
plate.
PRINCIPLE
When the current is fed to the coil magnetic force is
generated in iron, which attracts any other iron.
CONSTRUCTION
A magnetic clutch consists of a stator, rotor with pul-
ley, and pressure plate to engage the drive pulley
and compressor magnetically. The stator is fixed on
the compressor housing, and the pressure plate is
attached to the compressor shaft. Two ball bearings
are used between the inner surface of the rotor and
the front housing of the compressor.
OPERATION
Whenever the engine is operating, the pulley is rotat-
ing since it is connected to the crankshaft by a belt,
but the compressor does not operate until the clutch
is energized. When the air conditioning system is
switched ON, the ECU generates a signal for ener-
gizing the compressor. The electromagnet attracts
the pressure plate and pulls the plate against the
friction facings on the pulley. The friction between
the facing and plate causes the clutch assembly to
rotate as a unit, and drive the compressor.