Electrically Heated Systems; Rear Glass Heating Grid - Jeep Wrangler 1997 Manual

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CONTENTS
page ,
GENERAL INFORMATION
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 1
DESCRIPTION AND OPERATION
DEFOGGER RELAY . . . . . . . . . . . . . . . . . . . . . . . 2
DEFOGGER SWITCH . . . . . . . . . . . . . . . . . . . . . . 2
INSTRUMENT CLUSTER . . . . . . . . . . . . . . . . . . . 2
REAR GLASS HEATING GRID . . . . . . . . . . . . . . 1
DIAGNOSIS AND TESTING
DEFOGGER RELAY . . . . . . . . . . . . . . . . . . . . . . . 3
GENERAL INFORMATION
INTRODUCTION
An electrically heated rear window defogger is
standard factory-installed equipment on models
equipped with the hardtop option . The defogger will
only operate when the ignition switch is in the On
position . When the defogger switch is turned On, an
electric heater grid on the rear window glass is ener-
gized. This grid will produce heat to help clear the
window glass of ice, snow, or fog .
The defogger system is controlled by a switch
located in the accessory switch bezel, which is near
the bottom of the instrument panel center bezel and
next to the ash receiver . An amber indicator lamp in
the switch button will light to indicate when the
defogger system is turned on . The instrument cluster
circuitry, which contains the defogger system timer
logic, monitors the state of the defogger switch
through a hard-wired input . The instrument cluster
circuitry controls the defogger system through a
hard-wired control output to the defogger relay.
The defogger system will be automatically turned
off after a programmed time interval of about ten
minutes . After the initial time interval has expired, if
the defogger switch is turned on again during the
same ignition cycle, the defogger system will auto-
matically turn off after about five minutes .
The defogger system will automatically shut off if
the ignition switch is turned to the Off position, or it
can be turned off manually by depressing the instru-
ment panel switch . Refer to the owner's manual for
more information on the defogger system controls
and operation .
Following are general descriptions of the major
components in the defogger system . Refer to 8W-48 -
ELECTRICALLY HEATED SYSTEMS 8N - 1
ELECTRICALLY HEATED SYSTEMS
page
DEFOGGER SWITCH . . . . . . . . . . . . . . . . . . . . . . 3
DEFOGGER SYSTEM . . . . . . . . . . . . . . . . . . . . . 2
INSTRUMENT CLUSTER . . . . . . . . . . . . . . . . . . . 4
REAR GLASS HEATING GRID . . . . . . . . . . . . . . 3
SERVICE PROCEDURES
REAR GLASS HEATING GRID REPAIRS . . . . . . . 5
REMOVAL AND INSTALLATION
DEFOGGER RELAY . . . . . . . . . . . . . . . . . . . . . . . 6
DEFOGGER SWITCH . . . . . . . . . . . . . . . . . . . . . . 5
Rear Window Defogger in Group 8W - Wiring Dia-
grams for complete circuit descriptions and diagrams .
NOTE: This group covers both Left-Hand Drive
(LHD) and Right-Hand Drive (RHD) versions of this
model . Whenever required and feasible, the RHD
versions of affected vehicle components have been
constructed as mirror-image of the LHD versions.
While most of the illustrations used in this group
represent only the LHD version, the diagnostic and
service procedures outlined can generally be
applied to either version . Exceptions to this rule
have been clearly identified as LHD or RHD, if a
special illustration or procedure is required.
DESCRIPTION AND OPERATION
REAR GLASS HEATING GRID
The heated rear window glass has two electrically
conductive vertical bus bars and a series of horizon-
tal grid lines made of a silver-ceramic material,
which is baked on and bonded to the inside surface of
the glass . The grid lines and bus bars comprise a
parallel electrical circuit .
When the rear window defogger relay is energized,
electrical current is directed to the rear window grid
lines through the bus bars. The grid lines heat the
rear window to clear the surface of fog or snow. Pro-
tection for the heated grid circuit is provided by a
fuse in the Power Distribution Center.
The grid lines and bus bars are highly resistant to
abrasion. However, it is possible for an open circuit
to occur in an individual grid line, resulting in no
current flow through the line . The grid lines can be
damaged or scraped off with sharp instruments . Care
should be taken when cleaning the glass or removing