Buick LeSabre 1965 Service Manual page 617

ELECTRICAL SYSTEMS
HEADLIGHTS AND CONTROLS 1 0 - 4 7
SECTION 10-F
LIGHTING SYSTEM
CONTENTS OF SECTION 10-F
Paragraph
Subject
10-41 Headlights & Controls
10-42 Headlamp Sealed Beam
Unit Replacement and
Adjustment
Page
10-47
10-49
Paragraph Subject
10-43 Parking, Tail, Stop, License,
Back-up & Trunk Lights .
10-44 Interior Lights and Cigar
Lighters
Page
10-49
10-51
1 0 - 4 1 HEADLIGHTS AND
CONTROLS
a. Description of Lighting
Switch
The switch u s e s a multiple
push-on type connector. It is a
"push-pull" type which also in-
corporates a manually operated
rheostat for controlling the in-
strument panel lights, and a de-
tent position which completes the
dome light circuit. Three "push-
pull" positions of the switch knob
provide control of the exterior
lights as follows:
1. Off position (knob all the way
in) cuts off all lights controlled by
the switch.
2. Parking position (knob pulled
out to first notch) turns on the
parking lights, tail lights, and
license light and key light. The
instrument panel lights also will
be turned on if the rheostat is
set for these lights.
3. Driving position (knob pulled
out to last notch) turns parking
lights off and turns headlights on,
while the other lights remain as
in the parking position. The head-
lights will be on the upper or
lower beams depending on the po-
sition of the separate dimmer
switch.
In the parking and driving po-
sitions, t h e instrument p a n e l
lights are controlled by rotating
the light switch knob. With the
knob t u r n e d counterclockwise,
these lights are on maximum
brightness. As the knob is turned
clockwise, they gradually dim un-
til they are off at the full clock-
wise position of the knob.
4. Dome l i g h t position (knob
turned f u l l y counterclockwise)
turns the dome light on. The dome
light can be turned on regardless
of the in-or-out position of the
switch.
b. Description of Thermo
Circuit Breaker
A thermo circuit breaker is in-
corporated in the lighting switch
assembly, to protect wiring from
damage due to short circuits in
the headlight and front parking
light circuits only.
The thermo circuit breaker con-
sists of a bi-metal blade and set
of contact points connected in
series with the lighting circuits.
An abnormal flow of current
through the circuit breaker, such
as would be caused by a short
circuit in a lighting circuit, heats
the bi-metal blade sufficiently to
separate the points and cause
them to vibrate. The vibrating
blade alternately opens and closes
the circuit, thus reducing the flow
of current and protecting the wir-
ing against overheating and burn-
ing. The flickering light produced
by the vibrating circuit breaker
serves as a warning to the op-
erator of vehicle that a short
circuit exists.
c. Test of Lighting Switch
If the lighting switch is suspected
of being faulty, the contacts can
be tested by connecting a low
reading voltmeter between the
wire supplying current to the con-
tact and the wire conducting cur-
rent away. This must be done
with the switch in a position
where the contact under test is
closed. See Figure 10-52.
1. In order to gain access to the
headlight switch, r e m o v e the
instrument panel cover.
2. To check the switch contact
for the headlights, pull switch
knob out to last notch and also
make sure dimmer switch is in
upper beam position. Connect
voltmeter prods between battery
and headlight terminals of switch
(between red and light blue wires).
TO FRONT PARKING LIGHTS-
TO HEAD LIGHTS
FROM "TAIL LIGHTS"
FUSE
TO TAIL LIGHTS
TO "PANEL LTS."
FUSE AND
PANEL LIGHTS
FROM BATTERY
TO DOME LIGHT
GROUND CONTACT
Figure 10-52—Lighting Switch-
Bottom Side