The headlight relay receives battery voltage at all
times. When you turn the headlight switch to the
HEAD position with the dimmer switch in LOW,
ground is applied through the BLU/RED wire to the
coil of the headlight relay. The relay is then
energized, applying battery voltage to the left and
right high and low beam headlights through fuses
45 and 46. The low beam bulbs come on because
the opposite terminal is tied to ground through the
dimmer relay. The high beams and indicator remain
off because their ground path is interrupted by the
deenergized dimmer relay.

High Beams

When you pull the dimmer switch to HIGH with the
low beams already on, ground is applied to the
dimmer relay from the dimmer switch. This
energizes the dimmer relay, applying ground to the
high beam bulbs and high beam indicator, which
turns on the high beams and indicator light. The low
beams go off because their ground path is
interrupted by the activated dimmer relay.

Flash-to-Pass

When you hold the flash-to-pass switch in the ON
position, ground is applied through the BLU/RED
wire to the coil of the headlight relay and through
the RED/BLU wire to the coil of the dimmer relay.
This energizes the headlight relay, applying battery
voltage to the low and high beam bulbs and to the
dimmer relay. As the high beam bulbs receive
battery voltage, the dimmer relay is energized,
applying ground to the high beam bulbs and high
beam indicator, which turns on the high beams and
indicator light. The low beams go off because their
ground path is interrupted by the activated dimmer
relay.

Automatic Lighting

When you move the headlight switch to the AUTO
position, the automatic lighting control unit will
automatically turn on the headlights.

The automatic lighting control unit receives battery
voltage through fuse 56 at all times and receives
battery voltage through fuse 20 with the ignition
switch in ON (ll) and START (lll). When the ignition
switch is turned to ON (ll), the automatic lighting
control unit receives an “ignition on” signal through
fuse 19. When the headlight switch is in the AUTO
position with the driver’s door closed, and if the
automatic lighting sensor detects low ambient light,

the automatic lighting control unit will apply ground
to the BLU/RED wire and ground the headlight
relay. The relay energizes and causes the high or
low beam headlights to come on, depending on the
position of the dimmer switch. The headlights will
operate as if they had been turned on with the
headlight switch. When the driver’s door is open,
ground is applied to the automatic lighting control
unit through the GRN/BLU wire. When the control
unit receives this ground signal, it removes ground
from the headlight relay and causes the headlights
to turn off. The automatic lighting control unit will
also turn off the headlights if the ambient light levels
rise to daylight conditions or if the headlight switch
is moved out of the AUTO position.

Refer to the Service Manual (Section 23, Electrical) for
specific tests and troubleshooting procedures.

2004 American Honda Motor Co., Inc.

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