Heater

Battery voltage is applied at all times to the Heater Circuit Breaker. Battery voltage is also applied to the coil of the Heater Relay whenever the ignition switch is in "ON." When the BLOWER SWITCH is moved to "LO," the coil of the Heater Relay is grounded, the relay is energized and Battery voltage is applied through the Heater Circuit Breaker and the closed contacts of the Heater Relay to the BLOWER MOTOR. With the BLOWER SWITCH in "LO," current must travel all the way through the resistive element in the BLOWER RESISTOR before the BLOWER MOTOR can receive a ground at G203 in JUNCTION BLOCK 4. Therefore, the reduced voltage potential caused by the BLOWER RESISTOR maintains the BLOWER MOTOR at low speed.

When the BLOWER SWITCH is in the M1 position, the BLOWER MOTOR'S ground path passes only partially through the BLOWER RESISTOR and then through the BLOWER SWITCH before reaching ground at G2O3 in JUNCTION BLOCK 4. Since less of the BLOWER RESISTOR is in the circuit, the resistance in the circuit is lower and, in turn, the voltage potential of the circuit is higher. Therefore, the BLOWER MOTOR operates at a higher speed than it does with the BLOWER SWITCH in the "LO" position.

M2 operation is identical to Ml operation with the exception that even less of the BLOWER RESISTOR is in the circuit. Therefore, BLOWER MOTOR operation in M2 is faster than it is in Ml.

With the BLOWER SWITCH in "HI," the ground path of the BLOWER MOTOR bypasses the BLOWER RESISTOR entirely and passes directly through the BLOWER SWITCH to G2O3 in JUNCTION BLOCK 4. Therefore, the resistance in the ground path is nearly zero and the BLOWER MOTOR operates on full Battery voltage. This negligible resistance and, in turn, higher voltage potential causes the BLOWER MOTOR to operate at full speed.