Mitsubishi Galant. Manual — part 644

RADIO WITH TAPE PLAYER AND CD PLAYER

TSB Revision

CHASSIS ELECTRICAL

54A-129

Inspection Procedure 8: Broadcasts can be heard but both AM and FM have a lot of noise.

DIAGNOSIS

STEP 1. Check that the noise occurs when the
engine is stopped or the engine is running.

Q: Does noise occur when the engine is stopped or

the engine is running?
When the engine is stopped :

Go to Step 2.

When the engine is running :

Check the vehicle's

noise suppressor. (Refer to Inspection
Procedure 10

P.54A-130

.)

STEP 2. Check that the following actions
disappear the noise.
(1) Tune to a station with a stronger wave.
(2) Extend the antenna completely (Mast antenna).
(3) Adjust the sound quality to suppress high tones.

Q: Is the noise eliminated?

YES :

Consult the radio manufacturer's service

center.

NO :

Go to Step 3.

STEP 3. Check that the radio is correctly
grounded.

Q: Is the radio correctly grounded?

YES :

Go to Step 4.

NO :

Consult the radio manufacturer's service
center.

STEP 4. Check that the antenna plug is properly
connected to the radio.

Q: Is the antenna plug properly connected to the

radio?
YES :

Go to Step 7.

NO :

Go to Step 5.

STEP 5. Check that the noise is eliminated when
the antenna plug is properly attached.

Q: Is the noise eliminated?

YES :

Consult the radio manufacturer's service

center.

NO :

Go to Step 6.

STEP 6. Check that the antenna is in good
condition and is properly mounted.

Q: Is the antenna in good condition and is it properly

mounted?
YES :

Consult the radio manufacturer's service

center.

NO :

Go to Step 7.

STEP 7. Clean the antenna plug and ground wire
mounting area. Mount the antenna securely.

NOTE: Noise encountered during FM reception only
due to differences in FM and AM system, FM is not
as susceptible as AM to interference from engines,
power lines, lighting, etc. On the other hand, due to
the characteristics of FM waves, there are
sometimes cases of noise or distortion which are
generated by typical noise interference (first fading
and multipath). (Refer to Inspection Procedure 6

P.54A-127

.) <Noise (hissing) occurs in weak signal

areas such as mountainous regions, but this is not
due to a problem with the radio.>

NOTE: Furthermore, the amount of interference will
be comparatively less for vehicles equipped with a
diversity antenna system*. If there is an equivalent
amount of distortion in vehicles or radios of the same
type, then differences will be because of differences
in antenna systems, and this should be explained to
the user.

NOTE: Diversity antenna system*: A system where
two types of antenna (glass main antenna and glass
sub antenna) are equipped and the antenna that
provides the best reception car be selected.

Q: Is the antenna in good condition?

YES :

Consult the radio manufacturer's service

center.

NO :

Clean or repair it. Check the noise is
eliminated. If the noise is not eliminated,
consult the radio manufacturer's service
center.

Inspection Procedure 9: There is more noise on either AM or FM.

DIAGNOSIS
There is much noise only on AM. Due to differences

in AM and FM systems, AM is more susceptible to
noise interference.

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CHASSIS ELECTRICAL

RADIO WITH TAPE PLAYER AND CD PLAYER

54A-130

STEP 1. Check that there is noise under the
following state(s).

•

A motorcycle was passing.

•

Lighting was flashing.

•

A vehicle passed close by, but it appeared to be a
vehicle generating a particularly large amount of
noise radiation.

•

Passed beneath a power line.

•

Passed beneath a telephone line.

•

Passed close by a signal generator.

•

Passed close by some other sources of electrical
noise.

•

Passed under a bridge.

Q: Is there noise in the above states?

YES :

Go to Step 3.

NO :

Go to Step 2.

STEP 2. Continue to check for static; when static
is detected, check for the conditions listed
above.

Q: Is there noise in the state described in Step 1?

YES :

Go to Step 3.

STEP 3. Check noise prevention on the radio side
is difficult.

Q: Is the noise level worse than other radios?

YES :

Consult a service center.Noise encountered

during FM reception only. Due to differences
in FM and AM systems, FM is not as
susceptible as AM to interference from
engines, power lines, lighting, etc. On the
other hand, due to the characteristics of FM
waves, there are sometimes cases of noise
or distortion which are generated by typical
noise interference (first fading and
multipath). (Refer to Inspection Procedure 8

P.54A-129

.) <Noise (hissing) occurs in

weak signal areas such as mountainous
regions, but this is not due to Furthermore,
the amount of interference will be
comparatively less for vehicles equipped
with a diversity antenna system*. If there is
an equivalent amount of distortion in
vehicles or radios of the same type, then
differences will be because of differences in
antenna systems, and this should be
explained to the user. a problem with the
radio. >Furthermore, the amount of
interference will be comparatively less for
vehicles equipped with a diversity antenna
system*. If there is an equivalent amount of
distortion in vehicles or radios of the same
type, then differences will be because of
differences in antenna systems, and this
should be explained to the user.

NO :

f the noise level is roughly the same as
other radios, there is no action to be taken.

Inspection Procedure 10: There is noise when starting the engine.

DIAGNOSIS

CAUTION

•

Connecting a high tension cable to the noise
filter may destroy the noise filter and should
never be done.

•

Check that there is no external noise. Since
failure to do this may result in an incorrect
diagnosis due to the inability to identify the
noise source, this operation must be
performed.

•

Noise prevention should be performed by
suppressing strong sources of noise step by
step.

NOTE: Capacitor: The capacitor does not pass DC
current, but as the number of waves increases when
it passes AC current, impedance (resistance against
AC) decreases, and current flow is facilitated. A
noise suppressing capacitor which take advantage of
this property is inserted between the power line for
the noise source and the ground. This suppresses
noise by grounding the noise component (AC or
pulse signal) to the body of the vehicle.

RADIO WITH TAPE PLAYER AND CD PLAYER

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CHASSIS ELECTRICAL

54A-131

NOTE: Coil: The coil passes DC current, but
impedance rises as the number of waves increases
relative to the AC current. A noise suppressing coil
which takes advantage of this property is inserted
into the power line for the noise source, and works by
preventing the noise component from flowing or
radiating out of the line.

NOISE TYPE SOUNDS
ARE IN PARENTHESES

CONDITIONS

CAUSE

REMEDY

AM, FM: ignition noise
(popping, snapping,
cracking, buzzing)

•

Increasing the engine
speed causes the
generator whine
sound to speed up
and the volume to
decrease.

•

Disappears when the
ignition switch turned
to "ACC".

•

Mainly due to the
spark plugs

•

Due to engine noise

•

Check or replace the
ground cable.

•

Check or replace the
noise capacitor

Other electrical
components

-

Noise may occur as the
electrical components
become older.

Repair or replace the
electrical components.

Static electricity (cracking,
crinkling)

•

Disappears when the
vehicle is completely
stopped.

•

Severe when the
clutch is engaged.

Occurs when parts or
wiring move for some
reason and contact metal
parts of the body.

Return parts or wiring to
their proper position.

Static electricity (cracking,
crinkling)

•

Various noise are
produced depending
on the body part of the
vehicle.

Due to removal of the
front hood, bumpers,
exhaust pipe and muffler,
suspension, etc.

Ground parts by bonding.
Cases where the
problem is not eliminated
by a signal response to
one area are common,
due to several body parts
being imperfectly
grounded.

AC001346AC

<2.4L ENGINE>

GROUND CABLE

FRONT DECK

AC001348

<3.0 L ENGINE>

FRONT DECK

GROUND CABLE

AC

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CHASSIS ELECTRICAL

RADIO WITH TAPE PLAYER AND CD PLAYER

54A-132

Inspection Procedure 11: Some noise appears when there is vibration or shocks during traveling.

DIAGNOSIS

STEP 1. Check that the connectors are properly
connected.

NOTE: For the corresponding connectors, etc., refer
to GROUP 90, Audio System <vehicles with four
speakers

P.90-132

> or <vehicles with seven

speakers

P.90-134

>.

Q: Are the connectors properly connected?

YES :

Go to Step 2.

NO :

Check the condition of the connector. Refer
to GROUP 00E, Harness Connector
Inspection

P.00E-2

. Check that there is no

noise.

STEP 2. Check that noise appears when the radio
switch is turned on while the vehicle is stopped.

NOTE: Static electricity noise: Body static electric
from the shock absorber rubber bushings used to
prevent vibration, tires, etc. occurs because of
separation from the ground, causing a buzzing noise.
Since no measures can be taken to discharge the
static electricity of the vehicle body. Check that there
is no noise.

Q: Does noise appear when the radio switch is turned

on while the vehicle is stopped?
YES :

Go to Step 3.

NO :

It may be static electricity noise.

STEP 3. Check that the radio is correctly
grounded.

Q: Is the radio correctly grounded?

YES :

Go to Step 4.

NO :

Tighten the screw securely. Check that
there is no noise.

STEP 4. Check that the antenna is correctly
grounded. (If noise appears when the antenna is
moved, this means the ground is not securely
connected.)

Q: Is the antenna correctly grounded?

YES :

Repair or replace the radio. Check that

there is no noise.

NO :

If rust is present on the antenna ground
screw, clean off the rust and tighten the
ground screw securely. Check that there is
no noise.

Inspection Procedure 12: Noise Sometimes Appears on FM During Traveling.

Radio and CD Player Circuit
Refer to GROUP 90, Audio System <vehicles with
four speakers

P.90-132

> or <vehicles with seven

speakers

P.90-134

>.

AC001347

<2.4L ENGONE>

BATTERY

NOISE CAPACITOR

AC

AC003692

NOISE CAPACITOR

<3.0L ENGINE>

INTAKE MANIFOLD

AB