Heating and Air Conditioning: Description and Operation

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

* Low speed operation
(USA)
When the blower SW is moved to LO position, the current flows to TERMINAL 1 of the blower SW to TERMINAL 8 to GROUND, causing the HEATER relay to come ON. Then the current from ALT fuse flows to TERMINAL 1 of the HEATER relay to TERMINAL 2 to HEATER fuse to TERMINAL 2 of the blower motor to TERMINAL 1 to TERMINAL 4 of the blower resistor to TERMINAL 1 to GROUND, causing the blower motor to rotate. At this time, the current flows against the full resistance of the blower resistor, so the motor turns slowly at low speed.

(CANADA)
When the blower SW is moved to LO position, the current flows to TERMINAL 1 of the blower SW to TERMINAL 8 to GROUND, causing the HEATER relay to come ON. Then the current from ALT fuse flows to HEATER fuse to TERMINAL 1 of the HEATER relay to TERMINAL 2 to TERMINAL 2 of the blower motor to TERMINAL 1 to TERMINAL 4 of the blower resistor to TERMINAL 1 to GROUND, causing the blower motor to rotate. At this time, the current flows against the full resistance of the blower resistor, so the motor turns slowly at low speed.

* Medium speed operation (Operation at speed M1, M2)
When the blower SW is moved to the M1 position, the current flows to TERMINAL 1 of the blower SW to TERMINAL 8 to GROUND, turning the HEATER relay to ON. Then, the same as low speed operation, the current passing through the HEATER fuse (USA) or TERMINAL 2 of the HEATER relay (Canada) flows to the TERMINAL 2 of the blower motor to TERMINAL 1 to TERMINAL 4 of the blower resistor to TERMINAL 3 to TERMINAL 3 of the blower SW to TERMINAL 8 to GROUND. At this time, the blower resistance of the blower resistor is less than at low speed, so the blower motor rotates at medium low speed.

When the blower SW is moved to M2 position, the current flowing through the blower motor flows from TERMINAL 4 of the blower resistor to TERMINAL 2 to TERMINAL 2 of the blower SW to TERMINAL 8 to GROUND. At this time, blower resistance of the blower resistor is less than at M1 position, so the blower motor rotates at medium high speed.

* High speed operation
When the blower SW is moved to HI position, the current flows to TERMINAL 1 of the blower SW to TERMINAL 8 to GROUND, turning the HEATER relay to ON. Then, the same as medium speed operation, the current passing through the blower motor flows from TERMINAL 6 of the blower SW to TERMINAL 8 to GROUND, causing the blower motor to rotates at high speed.

2. AIR CONDITIONING OPERATION
When the blower SW is set to ON, current from the ALT fuse flows through the HEATER fuse and A.C fuse to TERMINAL 1 of the A(C dual pressure SW to TERMINAL 2 to TERMINAL 1 of the A/C amplifier. The engine speed signal from igniter and the evaporator temp. signal from the A/C thermistor are all supplied to the A/C amplifier. When the A/C SW is turned ON, the A/C SW ON signal is sent to activate the A/C amplifier. Current flows from the A/C amplifier to the 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.