Metro L3-061 1.0L VIN 6 TBI (1998)
Control Module HVAC: Description and Operation
Blower Controls
Battery voltage is applied through the HEATER fuse to the blower speed selector switch when the ignition switch is in the ON position. When the
blower speed selector switch is moved to the LOW position system voltage is applied through the closed contacts of the blower speed selector switch.
With the blower speed selector switch in the LOW position the current must travel all the way through the resistive element in the blower motor resistor
before traveling to ground through the blower motor. The voltage reduction caused by the blower motor resistor maintains the blower motor at LOW
speed.
When the blower speed selector switch is in the M1 position voltage passes partially through the blower motor resistor before reaching ground through
the blower motor. The circuit resistance is lower because less of the blower motor resistor is part of the circuit. The voltage potential at the blower motor
is therefore higher causing the blower motor to operate at a higher speed than in the LOW position.
The M2 operation is identical to the M1 operation with the exception that even less of the blower motor resistor is in the circuit. The blower motor
operation in M2 is faster than the operation is in M1.
With the blower speed selector switch in the HIGH position the voltage bypasses the blower motor resistor entirely. The voltage passes directly through
the blower motor to ground. Since the resistance in the ground path is nearly 0, the blower motor operates on full system voltage and at full speed.
