Turn Signal And Hazard Warning Systems Diagnosis And Testing - Jeep 200 Cherokee Service Manual

8J - 4 TURN SIGNAL AND HAZARD WARNING SYSTEMS
DESCRIPTION AND OPERATION (Continued)
Fig. 2 Combination Flasher - Typical
will become high and the IC signals the PNP transis-
tor to de-energize the circuit. This cycling will con-
tinue until the right or left turn signal switch is
turned off.
A special design feature of the combination flasher
allows it to "sense" 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 "senses" 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.
DIAGNOSIS AND TESTING
TURN SIGNAL AND HAZARD WARNING
SYSTEMS
When diagnosing the turn signal or hazard warn-
ing circuits, remember that high generator output
can burn out bulbs rapidly and repeatedly. If this is a
problem on the vehicle being diagnosed, refer to
Charging System in the Diagnosis and Testing sec-
tion of Group 8C - Charging System for further diag-
nosis of a possible generator overcharging condition.
If the problem being diagnosed is related to a fail-
ure of the turn signals to automatically cancel follow-
ing completion of a turn, inspect the multi-function
switch for a faulty or damaged cancel actuator and
inspect the turn signal cancelling cam lobes on the
clockspring mechanism for damage or improper
installation. For complete circuit diagrams, refer to
Turn Signals in the Contents of Group 8W - Wiring
Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL,
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Turn the ignition switch to the On position.
Actuate the turn signal switch or the hazard warning
switch. Observe the turn signal indicator lamp(s) in
the instrument cluster. If the flash rate is very high,
check for a turn signal bulb that is not lit or is very
dimly lit. Repair the circuits to that lamp or replace
the faulty bulb, as required. If the turn signal indi-
cator(s) fail to light, go to Step 2.
(2) Turn the ignition switch to the Off position.
Check the turn signal fuse in the junction block
and/or the hazard warning fuse in the Power Distri-
bution Center (PDC). If OK, go to Step 3. If not OK,
repair the shorted circuit or component as required
and replace the faulty fuse(s).
(3) Check for battery voltage at the hazard warn-
ing fuse in the PDC. If OK, go to Step 4. If not OK,
repair the open fused B(+) circuit to the battery as
required.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the turn signal fuse in
the fuseblock module. If OK, go to Step 5. If not OK,
repair the open fused ignition switch output (accesso-
ry/run) circuit to the ignition switch as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the combination flasher from its wire har-
ness connector and replace it with a known good
unit. Connect the battery negative cable. Test the
operation of the turn signal and hazard warning sys-
tems. If OK, discard the faulty combination flasher.
If not OK, remove the test flasher and go to Step 6.
(6) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (accessory/run) circuit cavity in the combina-
tion flasher wire harness connector. If OK, go to Step
7. If not OK, go to Step 9.
GROUP 8M - PASSIVE
STEERING COLUMN,
XJ
OR