Buick LeSabre 1965 Service Manual page 858

ACCESSORIES
ELECTRO-CRUISE 1 1 - 1 2 5
When the Electro-Cruise is in
operation at the desired set
speed, the cam which is mounted
to the input shaft oscillates the
cam follower to cause oscillation
of the contact pin. During one-
half of the oscillation, the contact
pin will contact the contact spring
to complete an electrical circuit
to the electronic control unit.
During the other one-half of the
oscillation, the contact spring is
held away from the contact pin by
the pickup arm to open the elec-
trical circuit to the electronic
control unit. The angle of contact
oscillation, or range of propor-
tional control corresponds to a
speed of 5 MPH and reflects a
square wave electrical impulse to
the electronic control unit. See
figure 11-175.
As car speed increases within
2-1/2 MPH above the set speed,
the pickup arm moves the con-
tact pin to allow the circuit to the
electronic control unit to remain
open for a greater interval of
time during one complete oscil-
lation. Whenever car speed is
more than 2-1/2 MPH above the
set speed, the circuit to the elec-
tronic control unit will be open
during the entire oscillation.
As car speed decreases within
2-1/2 MPH below the set speed,
the pickup arm moves away from
the contact spring to allow the
circuit to the electronic control
unit to remain closed for a
greater interval of time during
one complete oscillation. When-
ever car is less than 2-1/2 MPH
below set speed, the circuit to the
electronic control unit will be
closed during the entire oscilla-
tion. Thus, the electrical signal
which is reflected to the elec-
tronic control unit is proportional
to the interval of time during
which the contacts are open or
closed which, in turn, is propor-
tional to the amount the speed-
ometer pointer is above or below
the set speed.
3. AMPLIFIER AND RELAY -
The electronic control unit con-
sists of a relay assembly and a
transistor amplifier a s s e m b l y
mounted on a common junction
block which is an integral part of
the system's wiring harness. Both
assemblies are designed to in-
dividually plug into the junction
block; therefore, each can be
s e r v i c e separately. A two am-
pere fuse is incorporated into the
junction block to protect the
entire electrical circuitry of the
system. In addition, the system
is protected by the "BK" and
"BZ" fuse located in the main
fuse block. See figure 11-176.
The transistor amplifier serves
as a power amplifier to increase
the strength of the electrical sig-
nal from the speed transducer to
a value capable of operating the
power unit control valve. Since
full current flow is not carried by
the speed transducer contacts,
their life is greatly increased.
Design of the amplifier circuit is
such that whenever the speed
transducer contacts are closed,
the circuit through the amplifier
is completed and the power unit
coil is e n e r g i z e d . Likewise,
whenever the speed transducer
contacts are open, the circuit
through the amplifier is open and
the power unit coil is not
energized.
As long as the holding coil re-
mains energized to hold the con-
tact points in the Down position,
the system will be "locked" in
cruise operation and car speed
will be controlled by the power
unit in accord with the electrical
signal produced by the speed
transducer. Opening either the
ignition switch, the brake release
switch or the engagement switch
will "unlock" the system from
cruise operation by allowing the
relay contact points to return to
the "up" position.
Two opposing coils and a double
set of contact points within the
relay assembly function to con-
trol the "locking" and "unlock-
ing" of the system in cruise
operation. In addition, the relay
controls the operation of the
CRUISE lamp. See figure 11-176.
Figure 11-172—Electro-Cruise Controls - 49000 Series