Dodge 2000 DURANGO Service Manual page 311

DN
DESCRIPTION AND OPERATION (Continued)
cluster circuit board are faulty, the entire cluster
must be replaced. The cluster lens, the cluster hood,
the rear cluster housing cover, and the incandescent
lamp bulbs and holders are available for service
replacement.
OPERATION
GAUGE
With the ignition switch in the On or Start posi-
tions, voltage is supplied to all gauges through the
instrument cluster electronic circuit board. With the
ignition switch in the Off position, voltage is not sup-
plied to the gauges. The gauges do not accurately
indicate any vehicle condition unless the ignition
switch is in the On or Start positions.
All of the instrument cluster gauges, except the
odometer, are air core magnetic units. Two fixed elec-
tromagnetic coils are located within the gauge. These
coils are wrapped at right angles to each other
around a movable permanent magnet. The movable
magnet is suspended within the coils on one end of a
shaft. The gauge needle is attached to the other end
of the shaft.
One of the coils has a fixed current flowing
through it to maintain a constant magnetic field
strength. Current flow through the second coil
changes, which causes changes in its magnetic field
strength. The current flowing through the second coil
is changed by the instrument cluster electronic cir-
cuitry in response to messages received on the
Chrysler Collision Detection (CCD) data bus network.
The gauge needle moves as the movable permanent
magnet aligns itself to the changing magnetic fields
created around it by the electromagnets. The instru-
ment cluster circuitry is programmed to move all of
the gauge needles back to the low end of their respec-
tive scales after the ignition switch is turned to the
Off position.
INDICATOR LAMP
Indicator lamps are located in the instrument clus-
ter and are served by the cluster circuit board and
connectors. Many of the indicator lamps in the
instrument cluster are controlled by the instrument
cluster circuitry in response to messages received
over the Chrysler Collision Detection (CCD) data bus
network.
The four-wheel drive lock indicator lamp, head-
lamp high beam indicator lamp, low washer fluid
warning lamp, security lamp and turn signal indica-
tor lamps are hard wired. The seat belt reminder
lamp is controlled by the instrument cluster pro-
gramming and by CCD data bus messages from the
Airbag Control Module (ACM). The brake warning
lamp is controlled by a hard wired input from the
INSTRUMENT PANEL SYSTEMS
park brake switch and by CCD data bus messages
from the Controller Anti-lock Brake (CAB). The
instrument cluster circuitry uses CCD data bus mes-
sages from the Powertrain Control Module (PCM),
ACM, and CAB to control all of the remaining indi-
cator lamps.
In addition, certain indicator lamps in this instru-
ment cluster are programmable. This feature allows
those indicator lamps to be activated or deactivated
with a DRBIII scan tool through the instrument
cluster electronic circuitry for compatibility with cer-
tain optional equipment. The programmable indicator
lamps for this model include the cruise-on indicator
lamp, the overdrive-off indicator lamp, the transmis-
sion oil temperature warning lamp and the upshift
indicator lamp.
Except for the cruise-on indicator lamp, the head-
lamp high beam indicator lamp and the turn signal
indicator lamps, each of the indicator lamps in the
instrument cluster is illuminated by a dedicated
Light-Emitting Diode (LED). If an LED should fail,
the entire instrument cluster must be replaced. The
cruise-on indicator lamp is part of the odometer VFD
display. The headlamp high beam indicator lamp and
the turn signal indicator lamps use incandescent
bulbs and holders. Each incandescent indicator lamp
has a replaceable bulb and bulb holder.
CLUSTER ILLUMINATION LAMP
The cluster illumination lamps are hard wired in
the instrument cluster. When the park or head lamps
are turned on, the cluster illumination lamps light.
Illumination brightness is adjusted by rotating the
headlamp switch panel lamps dimmer thumbwheel
(down to dim, up to brighten). The instrument clus-
ter illumination lamps receive battery feed from the
panel dimmer circuitry in the headlamp switch
through a fuse in the junction block.
The instrument cluster electronic circuitry also
monitors the cluster illumination lamp dimming level
whenever the park or head lamps are turned on. The
instrument cluster electronic circuitry responds by
adjusting the dimming level of the instrument cluster
Vacuum Fluorescent Display(s) (VFD), and sending
dimming level messages over the Chrysler Collision
Detection (CCD) data bus network. All VFDs are illu-
minated at full brightness for improved daylight vis-
ibility whenever the park lamps or headlamps are
turned off.
Each of the cluster illumination lamps is located on
the instrument cluster circuit board. Each cluster
illumination lamp has a replaceable bulb and bulb
holder.
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