Jeep J-10 Series 1982 Technical & Service Manual page 303

Electronic Regulator
The electronic regulator is a sealed black box that
contains several electronic circuits.
The speed sensor, driven by the speedometer cable, is
a tach-generator that functions as the source for the
vehicle speed analog voltage. The AC voltage generated
by the sensor is applied to the amplifier section of the
regulator, which amplifies and shapes it. The amplified
voltage signal is further modified by the frequency-to-
DC converter, which transforms the variable AC voltage
into a DC voltage that is proportional to the vehicle
speed.
The DC voltage is applied to four circuits in the regu
lator for further action. The low speed switch circuit
compares the amplitude of the DC voltage with a refer
ence voltage that is equivalent to 30 mph (48 km/h). If
the DC voltage amplitude is greater than the reference
voltage amplitude, the engage/resume/accelerate cir
cuit of the system is activated. The vehicle speed DC
voltage is also applied to the high and low comparator
circuits and to the memory circuit.
When the SET pushbutton is depressed, the memory
circuit stores the amplitude of the DC voltage (equiva
lent to vehicle speed) for future reference. Two reference
voltages are produced by the memory circuit, one repre
sents the set speed plus 1/4 mph (0.4 km/h) and the
other represents the set speed minus 1/4 mph (0.4
km/h). The reference plus voltage is applied to the high
comparator circuit and the reference minus voltage is
applied to the low comparator circuit.
If the DC voltage amplitude from the DC converter
(representing vehicle speed) remains between the refer
ence plus and minus voltage amplitudes, the regulator
maintains the charge valve in the closed position. The
vent valve is also maintained in the closed position. In
this condition, the throttle is maintained in a fixed
position.
NOTE: In their closed position, the charge valve sole
noid is deenergized and the vent valve solenoid is
energized.
Whenever a road incline is encountered, vehicle speed
decreases, speed sensor output decreases and the DC
voltage amplitude from the DC converter also decreases
a proportional amount. This creates an error voltage
that will be detected within the low comparator circuit.
When the amplitude of this voltage drops below the low
CRUISE COMMAND 1H-3
comparator reference voltage (set speed minus 1/4 mph
or 0.4 km/h), the charge valve solenoid is energized, the
valve opens and the diaphragm moves to pull the chain
and throttle cable, and the throttle is opened further. As
the throttle moves, a throttle-position sensor (poten
tiometer) inside the servo is activated to provide feed
back voltage to both comparator circuits. Without it, the
throttle would continue to be opened further than neces
sary to maintain the set speed. The throttle-position
potentiometer feedback voltage eliminates the error
voltage by increasing the DC voltage applied to the com
parator circuits. When this voltage is increased to an
amplitude that is between the high and low reference
voltages, the charge valve solenoid is deenergized (valve
closed) and the throttle is maintained in its new posi
tion. In this manner, changes in throttle position are
proportional to the amount that vehicle speed differs
from the set speed. For over-speed conditions (such as
descending a hill), the operation is similar, except the
high comparator circuit and vent valve are involved. The
high comparator circuit detects the DC voltage ampli
tude increase (error voltage) from the DC converter and
deenergizes the vent valve solenoid (valve open), admit
ting atmospheric pressure. The throttle begins to close.
The throttle closing activates the throttle-position po
tentiometer and the feedback voltage eliminates the er
ror voltage when the vehicle speed decreases to the set
speed and the voltage amplitude to the comparator cir
cuits is again between the two speed reference voltage
amplitudes.
The high and low comparator circuits operate only
when the engage/resume/accelerate circuit is activated.
This is accomplished by depressing the SET pushbutton
or by sliding the control switch to the RESUME/ACCEL
position. When the SET pushbutton is depressed and
released, the memory is updated to store the amplitude
of the present vehicle speed voltage. The engage/
resume/accelerate circuit is deactivated by depressing
the brake (or clutch pedal with manual transmission), or
by the vehicle speed voltage decreasing to below the low
speed reference voltage (30 mph or 48 km/h).
DIAGNOSIS
To diagnose Cruise Command system malfunctions,
refer to the Service Diagnosis Chart and Testing.
Refer to Chapter 3C—Instrument Panels and Com
ponents for details of speedometer cable and gear
replacement.
Service Diagnosis
Condition
Possible Cause Correction
SYSTEM DOES NOT
ENGAGE IN"ON"
POSITION
(1)
(2)
Restricted vacuum hose or no
vacuum.
Control switch defective.
(1) Locate restriction or air leak
and repair.
(2) Replace switch.
v 80
80693A