Heating and Air Conditioning: Description and Operation

1. HEATER BLOWER MOTOR OPERATION
With the ignition SW ON, current from the GAUGE fuse flows to TERMINAL 3 of the HEATER relay to coil to TERMINAL 5 to TERMINAL 5 of the healer blower SW.

(Low speed operation)
When the heater blower SW is moved to the LO position, the current applied to TERMINAL 5 flows to TERMINAL 6 to GROUND, causing the HEATER relay to come ON Then the current from the ALT fuse flows to TERMINAL 1 of the HEATER relay to TERMINAL 2 to the HEATER fuse to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 2 of the blower resistor to TERMINAL 4 to GROUND. causing the blower motor to rotate.

This time, the current flows against the full resistance of the blower resistor, so the motor turns slowly at low speed. (Operation at speed M1, M2)

When the heater blower SW is moved to the speed M1 position, the current applied to TERMINAL 5 flows to TERMINAL 6 to GROUND, turning the HEATER relay 10 ON. Then, the same as with low speed, the current passing through the HEATER fuse to the blower motor to TERMINAL 2 of the blower resistor to TERMINAL 3 to TERMINAL 1 of the heater blower SW to TERMINAL 6 to GROUND. This time, the resistance of the blower resistor is less than it is for low speed, so the blower motor rotates faster than it does at low speed. With the heater blower SW in the M2 position, the current flow through the motor flows to TERMINAL 2 of the blower resistor to TERMINAL 1 to TERMINAL 2 of the heater blower SW to TERMINAL 6 to GROUND. This time, resistance of the blower resistor is less than for speed M1 so that the blower motor rotates even faster than for speed M1.

(High speed operation)
With the heater blower switch in HI position, until the HEATER relay comes ON and current flows to the blower motor, operation is the same as for speed M1 and M2. The current passing through the blower motor flows to TERMINAL 8 of the heater blower SW to TERMINAL 6 to GROUND without flowing through the blower resistor, so that the blower motor rotates at the fastest speed, high speed.

2. AIR CONDITIONING OPERATION
When the heater blower SW is set to ON, current from the ALT fuse flows through the HEATER relay to the A/C fuse to TERMINAL 1 of the A/C dual pressure SW to TERMINAL 4 to TERMINAL 3 of the A/C amplifier. The evaporator temp. a signal from the A/C thermistor is all supplied to the A/C amplifier. When the A/C SW or defroster mode SW is turned ON, the A/C SW or defroster mode SW ON signal is sent to activate the A/C amplifier. Current flows from the A/C amplifier to the A/C magnetic clutch, turning the compressor ON. The A/C operation is shut OFF when a signal indicating low evaporator temp., or abnormally high or low refrigerant pressure, is supplied while the engine high speed signal exists. when one of these signals is received, the amplifier shuts OFF the A/C operation.