Chrysler Town, Dodge Caravan. Manual - part 78
motors, and fuel pumps that have been found to be
potential sources of RFI or EMI.
OPERATION
There are two common strategies that can be used
to suppress Radio Frequency Interference (RFI) and
ElectroMagnetic Interference (EMI) radio noise. The
first suppression strategy involves preventing the
production of RFI and EMI electromagnetic signals
at their sources. The second suppression strategy
involves preventing the reception of RFI and EMI
electromagnetic signals by the audio system compo-
nents.
The use of braided ground straps in key locations
is part of the RFI and EMI prevention strategy.
These ground straps ensure adequate ground paths,
particularly for high current components such as
many of those found in the starting, charging, igni-
tion, engine control and transmission control sys-
tems. An insufficient ground path for any of these
high current components may result in radio noise
caused by induced voltages created as the high cur-
rent seeks alternative ground paths through compo-
nents or circuits intended for use by, or in close
proximity to the audio system components or circuits.
Preventing the reception of RFI and EMI is accom-
plished by ensuring that the audio system compo-
nents are correctly installed in the vehicle. Loose,
corroded or improperly soldered wire harness connec-
tions, improperly routed wiring and inadequate audio
system component grounding can all contribute to
the reception of RFI and EMI. A properly grounded
antenna body and radio chassis, as well as a shielded
antenna coaxial cable with clean and tight connec-
tions will each help reduce the potential for reception
of RFI and EMI.
REMOTE SWITCHES
DESCRIPTION
A remote radio control switch option is available on
some models. Two rocker-type switches are mounted
on the back (instrument panel side) of the steering
wheel spokes (Fig. 12). The switch on the left spoke
is the seek switch and has seek up, seek down, and
preset station advance functions. The switch on the
right spoke is the volume control switch and has vol-
ume up, and volume down functions. The switch on
the right spoke also includes a “mode” control that
allows the driver to sequentially select AM radio, FM
radio, cassette player, CD player or CD changer (if
equipped).
OPERATION
These switches are resistor multiplexed units that
are hard-wired to the Body Control Module (BCM)
through the clockspring. The BCM sends the proper
messages on the Programmable Communications
Interface (PCI) data bus network to the radio
receiver. For diagnosis of the BCM or the PCI data
bus, the use of a DRB III
t scan tool and the proper
Diagnostic Procedures manual are recommended. For
more information on the operation of the remote
radio switch controls, refer to the owner’s manual in
the vehicle glove box.
DIAGNOSIS AND TESTING - REMOTE
SWITCHES
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,
REFER
TO
ELECTRICAL,
RESTRAINTS
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING
COLUMN,
OR
INSTRUMENT
PANEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
Any diagnosis of the Audio system should
begin with the use of the DRB III
t diagnostic
tool. For information on the use of the DRB
III
t, refer to the appropriate Diagnostic Service
Manual.
Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
Fig. 12 Remote Radio Switch Operational View
1 - PRESET SEEK
2 - SEEK UP
3 - VOLUME UP
4 - MODE
5 - VOLUME DOWN
6 - SEEK DOWN
8A - 12
AUDIO
RS
RADIO NOISE SUPPRESSION COMPONENTS (Continued)