1975 Datsun 280z FSM - Spooled up Racing

ELECTRICAL CIRCUIT
The electrical system of the air
conditioner is designed to control the
ground circuit. In the following paragraphs
are described the operations of
the blower motor, compressor and
magnet valves.
BLOWER MOTOR
OPERATION
As the ignition switch is turned on,
a power relay for the air conditioner
closes, allowing the current from the
battery to the blower motor, resistor
and blower speed switch. When the
blower speed switch is turned on, a
ground circuit is completed and thus
the blower motor begins to rotate.
COMPRESSOR
OPERATION
The compressor circuit contains a
compressor relay. The solenoid energizing
circuit of the relay includes the
blower speed switch, a micro switch,
the thermostat and a pressure switch,
all connected in series. On-off operations
in these devices control current
to the compressor clutch. This circuit
also controls the magnet valve for the
fast idle actuator.
MAGNET VALVE (VACUUM
SOURCE) OPERATION
Air Conditioning
The vacuum source magnet valve is
operated in conjunction with the onoff
of the blower speed switch. This
valve controls vacuum supply to the
vacuum-operated system.
Relay
Two relays are used. One is in the
line between the blower motor and the
battery. When the ignition switch is set
at ON, the current flows through the
solenoid to the ground, that is, the
relay solenoid is energized so that the
relay contacts are closed and the current
flows to the blower motor.
The other relay is located in the
line on the way to compressor clutch.
The pressure switch, thermostat, micro
switch and blower speed switch are in
series connection in the line where the
solenoid branches off. The current
passes through the blower speed
switch to the same ground circuit as
the blower motor.
Blower speed switch
The blower speed switch is directly
actuated by the FAN lever. The current
passes through the resistor to the
blower motor; then it passes through
the blower speed switch to the ground.
The speed of the blower motor is
changed to four speeds with the FAN
lever's position.
Magnet valve
This valve is opened and closed
electrically by its electric solenoid.
Pressure switch
Installed in the receiver drier, the
pressure switch interrupts current to
the compressor clutch and stops the
compressor operation whenever system
pressure on the high pressure lines
builds up abnormally. See Figure
AC-4.
Micro switch
The micro switch is actuated by the
AIR lever. This switch is on only when
the AIR lever is set at A/C position.
Thermostat
The thermostat has one sensor,
which is located in the center of the
evaporator core of the evaporator
housing and which senses the temperature
of air forced out of the evaporator.
In the thermostat, the contact is
switched to ON and OFF according to
the change in the temperature sensed
by the sensor; in other words, the
current which is sent to the compressor
clutch is cut so as to stop the
compressor's operation and to maintain
steady the temperature of air
forced out. One of the control cables
from the TEMP lever changes the
temperature setting for operation of
the thermostat.
Compressor clutch
The compressor clutch engages and
disengages the clutch disc electrically
by the electric solenoid, and transmits
the engine speed to the shaft of the
compressor.
AC-15
A