Prizm L4-1800cc 1.8L DOHC (1993)
Blower Motor: Description and Operation
CIRCUIT OPERATION
Battery voltage is applied at all times through the Heater Fusible Link to the switch contact of the Heater Relay. Ignition voltage is applied to the
coil of the Heater Relay when the ignition switch is in the "ON" and "START" positions. When the Blower Speed Selector Switch is moved to any
position other than "OFF," the coil of the Heater Relay is provided with a ground through the Blower Speed Selector Switch and Junction Block 2
to G204. With power and ground provided, the relay energizes, its contacts close and voltage is applied to the Blower Motor. Blower Motor speed
is maintained by controlling the voltage potential to the Blower Motor. This is achieved by increasing/decreasing the resistance within the Blower
Motor's ground path.
With the Blower Speed Selector Switch in "LO," current must travel through the entire resistive element in the Blower Motor Resistor before the
Blower Motor's ground path is completed through the Blower Speed Selector Switch and Junction Block 2 to G204. This reduces the voltage
potential to the Blower Motor greatly and in turn causes the Blower Motor to run at low speed.
When the Blower Speed Selector Switch is in the M1 position, the Blower Motor's ground path travels only partially through the resistive element
in the Blower Motor Resistor before completing the ground path at G204 through the Blower Speed Selector Switch and Junction Block 2. Since
less of the Blower Motor Resistor is in the circuit, the resistance in the circuit is lower, thus making the voltage potential of the circuit higher.
Therefore, the Blower Motor operates at a higher speed than it does with the Blower Speed Selector Switch in the "LO" position.
M2 operation is identical to M1 operation with the exception that even less of the Blower Motor Resistor is in the circuit. Therefore, Blower
Motor operation in M2 is faster than it is in both M1 and "LO."
With the Blower Speed Selector Switch in "HI," the ground path of the Blower Motor bypasses the Blower Motor Resistor entirely and passes
directly through the Blower Speed Selector Switch and Junction Block 2 to G204. Therefore, the resistance in the ground path is nearly zero and
the Blower Motor operates on full system voltage. Under these conditions, the Blower Motor operates at full speed.
