Jeep Grand Cherokee Wj 2000 Manual - page 4
TURN SIGNAL CANCELLING CAM
DESCRIPTION
The turn signal cancelling cam is concealed within
the multi-function switch mounting housing on the
top of the steering column below the steering wheel
and the clockspring mechanism. The turn signal can-
celling cam consists of a molded plastic hub and disc
unit with two integral lobes. The upper lobe of the
turn signal cancelling cam has a hole that is used to
align it with another hole in the back of the multi-
function switch mounting housing. The inside diame-
ter of the turn signal cancelling cam hub has an
integral metal-reinforced plastic key that locks the
unit to a keyway in the upper steering column shaft.
The upper surface of the turn signal cancelling
cam features three holes, two round and one oblong.
These holes engage and key the cam unit to three
matching pins in the hub of the clockspring mecha-
nism. The hub of the clockspring and the turn signal
cancelling cam lobes rotate with the steering wheel.
The centered clockspring housing is then secured to
the multi-function switch mounting housing over the
top of the turn signal cancelling cam. The multi-func-
tion switch mounting housing is secured to the steer-
ing column and remains stationary.
The turn signal cancelling cam is serviced as a
unit with the multi-function switch mounting hous-
ing. The turn signal cancelling cam cannot be
repaired and, if faulty or damaged, the multi-func-
tion switch mounting housing unit must be replaced.
Refer to Clockspring in the Removal and Installa-
tion section of Group 8M - Passive Restraint Systems
for the clockspring service procedures.
OPERATION
The turn signal cancelling cam has two lobes
molded into it. When the turn signals are activated
by moving the left multi-function switch control stalk
to a detent position, a turn signal cancel actuator is
extended from the inside surface of the multi-func-
tion switch housing toward the turn signal cancelling
cam. When the steering wheel is rotated during a
turning maneuver, one of the two turn signal cancel-
ling cam lobes will contact the turn signal cancel
actuator, releasing the left multi-function switch con-
trol stalk from its detent and cancelling the turn sig-
nal event.
COMBINATION FLASHER
DESCRIPTION
The combination flasher is a smart relay that func-
tions as both the turn signal system and the hazard
warning system flasher. The combination flasher con-
tains active electronic Integrated Circuitry (IC) ele-
ments. This flasher is designed to handle the current
flow requirements of the factory-installed lighting. If
supplemental lighting is added to the turn signal
lamp circuits, such as when towing a trailer with
lights, the combination flasher will automatically try
to compensate to keep the flash rate the same.
The combination flasher is located in the junction
block, under the left end of the instrument panel in
the passenger compartment. Because of the active
electronic elements within the combination flasher, it
cannot be tested with conventional automotive elec-
trical test equipment. If the combination flasher is
believed to be faulty, test the turn signal system and
hazard warning system circuits as described in this
group. Then replace the combination flasher with a
known good unit to confirm system operation.
The combination flasher cannot be repaired or
adjusted and, if faulty or damaged, it must be
replaced. Refer to Turn Signals in the Contents of
Group 8W - Wiring Diagrams for complete circuit
diagrams.
OPERATION
The combination flasher has nine blade-type termi-
nals intended for the following inputs and outputs:
fused B(+), fused ignition switch output, left turn
switch sense, right turn switch sense, hazard switch
sense, left front turn signal circuit, right front turn
signal circuit, left rear turn signal circuit and right
rear turn signal circuit. Constant battery voltage is
supplied to the flasher so that it can perform the
hazard warning function, and ignition switched bat-
tery voltage is supplied for the turn signal function.
However, when the flasher is idle no current is
drawn through the module. The unit does not become
active until it is provided a signal ground from the
turn signal switch, hazard warning switch or the
Body Control Module (BCM).
The IC within the combination flasher (Fig. 2) con-
tains the logic that controls the flasher operation and
the flash rate. Typical flash rate is about ninety
flashes per minute. When a bulb is burnt out, or
when a circuit for a lamp is open, the turn signal
flash rate will increase to a minimum of 180 flashes
per minute. However, an open lamp circuit or burnt
out bulb does not change the hazard warning flash
rate.
Turn signal inputs that actuate the combination
flasher are low current grounds, each drawing a
maximum of 300 milliamperes. The turn signal
inputs are provided to the flasher through the junc-
tion block by the turn signal (left multi-function)
switch on the steering column. The hazard warning
signal input is a low current ground drawing a max-
imum of 600 milliamperes. The hazard warning
input can be provided through the junction block by
8J - 4
TURN SIGNAL AND HAZARD WARNING SYSTEMS
WJ
DESCRIPTION AND OPERATION (Continued)