Mitsubishi L200. Manual — part 728

RADIO AND CD PLAYER

CHASSIS ELECTRICAL

54A-279

Inspection Procedure 5: Noise appears at certain places when travelling.

DIAGNOSIS PROCEDURE

STEP 1. Check the noise occur when entering or
near a particular structure (building, tunnel,
mountain, etc).

Q: Does the noise occur when entering or near a

particular structure (building, tunnel, mountain,
etc.)?
YES :

Go to Step 3.

NO :

Go to Step 2.

STEP 2. After taking the following measures to
prevent the noise, check that no noise appears.
(1) Change to a different station with a stronger wave

to boost resistance to interference.

(2) Suppress high tones to reduce noise.

Q: Do the following measures eliminate the noise?

YES :

This diagnosis is complete.

NO :

Go to Step 4.

STEP 3. Ask the owner about the state of the
noise.
Find out the following information from the owner.

• Place where the noise occurs.

• Locality conditions (valley, mountain, etc).

• Name and frequency of stations affected by noise

Q: Which is the noise, vehicle noise or external

noise?
Vehicle noise :

It may not be possible to prevent

noise if the signal is weak. This diagnosis is
complete.

External noise :

In almost all cases, prevention on

the receiver side is impossible. Weak
signals especially are susceptible to
interference. Go to Step 4.

STEP 4. Check that there is no noise.

Q: Does noise still exist?

YES :

If there is more noise than on radios in other

vehicles, find out the noise condition and
the name and frequency of the receiving
stations from the owner, and consult with
the radio manufacturer's service centre.

NO :

Normal.

Inspection Procedure 6: Mixed with noise, only at night.

The following factors can be considered as possible
causes of noise appearing at night.
1. Factors due to signal conditions: Due to the fact

that long-distance signals are more easily
received at night, even stations that are received
without problem during the day may experience
interference in a general worsening of reception
conditions. The weaker a station is the more
susceptible it is to interference, and a change to
different station or the appearance of a beating
sound* may occur.
NOTE: Beat sound*: Two signals close in fre-
quency interfere with each other, creating a repeti-
tious high-pitched sound. This sound is generated
not only by sound signals but electrical waves as
well.

2. Factors due to vehicles noise: Alternator noise

may be a cause.

DIAGNOSIS PROCEDURE

STEP 1. Check that the noise still obvious even
when the lamps are off.

Q: Is the noise still obvious even when the lamps are

off?
YES :

Go to Step 2.

NO :

Go to Step 3.

Step 2. Check hat the following actions.
Tune to a station with a stronger wave.

Q: Is there more noise than on radio in other

vehicles?
YES :

Consult the radio manufacturer's service

centre.

NO :

This diagnosis is complete.

RADIO AND CD PLAYER

CHASSIS ELECTRICAL

54A-280

Step 3. Check that the noise fades away when the
vehicle harness is moved away from the radio (if
the harness is not in the proper position).

Q: Does the noise fade away when the vehicle

harness is moved any from the radio (If the
harness is not in the proper position)?

YES :

Repair the wiring harness.

NO :

If there is more noise than other radios,
consult the radio manufacturer's service
centre.

Inspection Procedure 7: Broadcasts can be heard but both AM and FM have a lot of noise.

DIAGNOSIS PROCEDURE

STEP 1. Check the state of the antenna.

Q: Is the mast antenna assembled?

YES :

Go to Step 2.

NO :

Assemble the mast antenna. Check to see
that the noise is gone.

STEP 2. Check that the noise occur 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 3.

When the engine is running :

Check the vehicle's

noise suppressor (Refer to Inspection
Procedure 7

P.54A-282

).

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

Q: Is the noise eliminated?

YES :

Consult the radio manufacturer's service

centre.

NO :

Go to Step 4.

STEP 4. Check that the radio is correctly earthed
The radio is connected to the earth with an assem-
bling screw.

Q: Is the radio correctly earthed?

YES :

Go to Step 5.

NO :

Assemble the radio and CD player into the
vehicle.

STEP 5. Check the connection of the antenna
plug and radio and CD player.

Q: Is the antenna plug thoroughly connected to the

radio and CD player?
YES :

Go to Step 7.

NO :

Go to Step 6.

STEP 6. Check that the noise is eliminated when
the antenna plug is properly attached.

Q: Is the noise eliminated?

YES :

This diagnosis is complete.

NO :

Go to Step 7.

STEP 7. Check that the antenna is in good
condition and is it properly mounted.

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

mounted?
YES :

Consult the radio manufacturer's service

centre.

NO :

Repair or replace the antenna.

Inspection Procedure 7: Broadcasts can be heard but both LW/MW/FM have a lot of noise.

DIAGNOSIS PROCEDURE

STEP 1. Check the state of the antenna.

Q: Is the antenna assembled?

YES :

Go to Step 2.

NO :

Repair or replace the antenna.

STEP 2. Check that the noise occur when the
engine is stopped or the engine is running.

Q: Does noise occur when the engine is stopped or

the engine is running?

RADIO AND CD PLAYER

CHASSIS ELECTRICAL

54A-281

When the engine is stopped :

Go to Step 3.

When the engine is running :

Check the vehicle's

noise suppressor (Refer to Inspection
Procedure 8

P.54A-282

).

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

Q: Is the noise eliminated?

YES :

This diagnosis is complete.

NO :

Go to Step 4.

STEP 4. Check that the radio is correctly earthed
The radio is connected to the earth with an assem-
bling screw.

Q: Is the radio correctly earthed?

YES :

Go to Step 5.

NO :

Assemble the radio and CD player into the
vehicle.

STEP 5. Check the connection of the antenna
plug and radio and CD player.

Q: Is the antenna plug thoroughly connected to the

radio and CD player?
YES :

Go to Step 7.

NO :

Go to Step 6.

STEP 6. Check that the noise is eliminated when
the antenna plug is properly attached.

Q: Is the noise eliminated?

YES :

This diagnosis is complete.

NO :

Go to Step 7.

STEP 7. Check that the antenna is in good
condition and is it properly mounted.

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

mounted?
YES :

Consult the radio manufacturer's service

centre.

NO :

Repair or replace the antenna.

RADIO AND CD PLAYER

CHASSIS ELECTRICAL

54A-282

Inspection Procedure 8: There is noise when starting the engine.

DIAGNOSIS PROCEDURE

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 per-
formed.

• Noise prevention should be performed by

suppressing strong sources of noise step by
step.

Noise type sounds are in
parentheses

Conditions

Cause

Remedy

AM/FM or FM/MW/LW:
ignition noise (popping,
snapping, cracking,
buzzing)

• Increasing the engine

speed causes the
alternator whine
sound to speed up
and the volume to
decrease

• Disappears when the

ignition switch turned
to "ACC".

• Due to engine noise

• Check or replace the

earth 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.

Earth 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
earthed.