Civic L4-1668cc 1.7L SOHC MFI (2003)
Blower Motor: Description and Operation
How the Circuit Works
The heater control panel controls the blower controls, air delivery, and A/C compressor controls automatically. With the ignition switch in ON (II),
battery voltage is supplied through fuse 14. The control unit is grounded at G502.
Blower Controls
You can manually select the fan speed by turning the fan control dial clockwise, from the OFF position. Turning the dial further clockwise increases the
fan's speed, which increases air flow.
Battery voltage is applied through fuse 14 to the blower motor relay contacts at all times. With the ignition switch ON (II), the blower motor relay in the
under-hood fuse/relay box is energized which feeds battery voltage to the blower motor. The blower power transistor controls the blower motor in all
speeds except HIGH. The blower power transistor is controlled by the heater control panel. When the control panel requests HIGH blower speed, the
blower power transistor grounds the blower motor which connects it directly to ground, making the blower run at high speed.