with an ISO-relay, or else component and vehicle
damage may occur.
The combination flasher has five blade-type termi-
nals intended for the following inputs and outputs:
Battery B+, Ignition B+, Ground, Turn Signal circuit,
and Hazard Warning circuit. Constant battery volt-
age and ground are supplied to the flasher so that it
can perform the hazard warning function, and igni-
tion switched battery voltage is supplied for the turn
signal function. Refer to 8W-52 - Turn Signals in
Group 8W - Wiring Diagrams for complete circuit
descriptions, diagrams and terminal function identi-
fication.
The IC within the combination flasher (Fig. 1) con-
tains the logic that controls the flasher operation and
the flash rate. Pin 6 of the IC receives a sense volt-
age from the hazard warning portion of the multi-
function switch. When the hazard switch is turned
on, the
9
hazard on sense
9
voltage will become low due
to the circuit being grounded through the turn signal
bulbs. This low voltage sense signals the IC to ener-
gize
the
flash
control
Positive-Negative-Positive
(PNP) transistor at a pre-calibrated flash rate or fre-
quency. Each time the PNP transistor energizes the
hazard warning circuit, the pin 6
9
hazard on sense
9
voltage will become high and the IC signals the PNP
transistor to de-energize the circuit. This cycling will
continue until the hazard warning switch is turned
off.
Likewise, pin 8 of the IC receives a sense voltage
from the turn signal portion of the multi-function
switch. When the left or right turn signal is turned
on, the
9
turn signal on sense
9
voltage will become low
due to the circuit being grounded through the turn
signal bulbs. This low voltage sense signals the IC to
energize the flash control PNP transistor at a pre-
calibrated flash rate or frequency. Each time the PNP
transistor energizes the turn signal circuit, the pin 8
9
turn signal on sense
9
voltage will become high and
the IC signals the PNP transistor to de-energize the
circuit. This cycling will continue until the right or
left turn signal is turned off.
A special design feature of the combination flasher
allows it to
9
sense
9
that a turn signal circuit or bulb
is not operating, and provide the driver an indication
of the condition by flashing the remaining bulbs in
the affected circuit at a higher rate (120 flashes-per-
minute or higher). Conventional flashers either con-
tinue flashing at their typical rate (heavy-duty type),
or discontinue flashing the affected circuit entirely
(standard-duty type). During turn signal operation,
the combination flasher IC compares normal battery
voltage input on pin 2 with the shunt resistor voltage
input on pin 7. If the IC
9
senses
9
that the voltage dif-
ference between pin 2 and pin 7 is different than the
pre-calibrated value of the IC, it will increase the
rate at which it signals the PNP transistor to ener-
gize the pin 1 output. Thus, the inoperative half (left
or right side) of the turn signal circuit will flash
faster.
Because of the active electronic elements within
the combination flasher, it cannot be tested with con-
ventional automotive electrical test equipment. If the
combination flasher is believed to be faulty, test the
turn signal and hazard warning system circuits as
described in this group. Then replace the combina-
tion flasher with a known good unit to confirm sys-
tem operation.
The combination flasher cannot be repaired and, if
faulty or damaged, it must be replaced.
TURN SIGNAL SWITCH AND HAZARD WARNING
SWITCH
The turn signal and hazard warning switches are
integral to the multi-function switch assembly. The
multi-function switch assembly is mounted to the left
side of the steering column (Fig. 2). This switch con-
tains circuitry for the following functions:
•
Turn signals
•
Hazard warning
•
Headlamp beam selection
•
Headlamp optical horn
•
Windshield wipers
•
Windshield washers.
The information contained in this group addresses
only the multi-function switch functions for the turn
signal and hazard warning circuits. For information
relative to the other switch functions, refer to the
proper group. However, the multi-function switch
cannot be repaired. If any function of the multi-func-
tion switch is faulty, or if the switch is damaged, the
entire switch assembly must be replaced.
Fig. 1 Combination Flasher - Typical
8J - 2
TURN SIGNAL AND HAZARD WARNING SYSTEMS
ZJ
DESCRIPTION AND OPERATION (Continued)
Содержание Colorado 1998
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