Mitsubishi Montero (2004+). Manual — part 551

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1. The signal becomes weak as the distance from

the station's transmission antenna increases. The
signal strength received depends on the signal
strength of the transmitting station and intervening
obstructions such as buildings and hills. Generally
speaking, the area of good reception is
approximately 20

− 25 km (12 − 16 miles) for

stereo reception, and 30

− 40 km (19 − 25 miles)

for monaural reception.

2. The signal will becomes weak when an area of

shadow from the transmitting antenna (places
where there are obstructions such as mountains
or buildings between the station transmitter and
the vehicle), and noise will appear. <This is called
first fading, and gives a steady buzzing noise.>

3. If a direct signal hits the antenna at the same time

as a signal reflected by obstructions such as
mountains or buildings, interference of the two
signals will generate noise. When moving, noise
will appear each time the vehicle's antenna
passes through this kind of obstructed area. The
strength and interval of the noise varies according
to the signal strength and the conditions of
deflection. <This is called multipath noise, and is a
repetitive buzzing.>

4. Since FM stereo transmission and reception has a

weaker field than monaural, it is often
accompanied by a hissing noise.

After taking measures to prevent the noise, check
that no noise occurs.
5. Change to a different station with a stronger wave

to boost resistance to interference.

6. Suppress high tones to reduce noise.
7. Extend antenna completely.
If there is noise, the following causes can be consid-
ered.
8. If due to vehicle noise: It may not be possible to

prevent noise if the signal is weak.

9. If due to external noise: In almost all cases,

prevention on the receiver side is not possible.
Weak signals especially are susceptible to
interference.

If there is more noise than on radios in other vehi-
cles, 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
center.

INSPECTION PROCEDURE 7: Sound mixed with Noise, Only at Night (AM).

The following can be considered as possible causes
of noise appearing only at night.
1. It is significantly easier to receive long-distance

signals at night. This means that even stations
that are received without a problem during the day
may experience important to remember that the
weaker station is more susceptible to interference.
The appearance of a beat sound may occur in the
evening. A beat sound is created when two
signals close in frequency interfere with each
other. A common sign of this type of interference
is a repetitious high-pitched sound that may over
power the desired radio station. This sound is
generated not only by sound signals but electrical
waves as well.

2. The changing system may also be a source of

noise. When diagnosing radio noise, do not over
look the possibility of a problem with the vehicles
generator.

DIAGNOSIS

STEP 1. Check the vehicles lighting system.

Q: Does the noise disappear when the vehicles

headlights are turned "OFF"?

YES :

Go to Step 2.

NO :

Go to Step 3.

STEP 2. Check that the following actions
disappear the noise.

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

center.

NO :

Check that there is no noise.

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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 :

Consult the radio manufacturer's service

center.

NO :

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

INSPECTION PROCEDURE 8: Noise is Overpowering both AM and FM.

DIAGNOSIS

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. Verify 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 11

P.54A-175

.)

STEP 3. Verify 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 4.

STEP 4. Verify that the radio is correctly
grounded

The radio is connected to the ground with an assem-
bling screw.

Q: Is the radio correctly grounded?

YES :

Go to Step 5.

NO :

Consult the radio manufacturer's service
center.

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. Verify 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 7.

STEP 7. Verify 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

center.

NO :

Either repair or replace the antenna
assembly. Check to see that the noise is
gone.

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INSPECTION PROCEDURE 9: Excessive Noise on AM and FM.

.

DIAGNOSIS
Radio reception can be affected by Radio Frequency
(RF) emissions from a variety of sources. The distur-
bance is even greater if the station is weak or poorly
tuned. FM reception is not as sensitive to distur-
bances as AM. AM reception is sensitive to electrical
disturbances such as power lines, lightening and
other types of similar electrical phenomena.

STEP 1. Check if the customer heard the noise
under any of the following conditions.

• A motorcycle was passing.

• Lighting was flashing.

• Passed beneath a power line.

• Passed beneath a telephone line.

• Passed by a signal generator.

• Passed by any other sources of electrical noise.

• Passed under a bridge or through a tunnel.

Q: Did the noise occur during any of the

circumstances listed above?

YES :

The observed noise is normal.

NO :

Go to Step 2.

STEP 2. Compare the customers radio to another
identical model.

Operate the radio in a vehicle with a known good
audio system of the same type as the customer's.

Q: Is there more noise on the customers radio?

YES :

Check all power and ground connections. If

all connections are in good condition,
consult the radio manufacturers service
center.

NO :

The observed noise is normal.

INSPECTION PROCEDURE 10: Noise is Detected with Engine Running.

.

DIAGNOSIS

CAUTION

• Never connect a noise filter to the high ten-

sion cable (spark plug wire). Spark plug wires
incorporate resistors which have the effect of
suppressing noise. If a spark plug wire is
found to be causing noise, it must be
replaced.

• Confirm that the noise is not from an external

source.

• Noise prevention should be performed by

suppressing strong sources of noise first.

NOTE: Voltage surges can be induced in the electri-
cal system by the collapse of a field (i.e. When power
is removed from the coil in an A/C compressor
clutch). This induced voltage surge will radiate a
Radio Frequency (RF) signal that is picked up by the

audio unit. In the case of the compressor clutch a
"pop" will be heard through the speakers. The capac-
itor, installed on this vehicle, will store the excess
voltage and prevent the production of RF noise. This
is because the capacitor will charge and discharge
as the voltage fluctuates. This has the effect of
"attracting" noise and bleeding it to ground without
interfering with the normal flow of current through the
system.

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DESCRIPTION OF NOISE CONDITIONS

CAUSE

SOLUTION

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

• Increasing the engine

speed causes the
generator whine to
speed up and the
volume to decrease.

• Disappears when the

ignition switch turned
to "ACC", and engine
is off.

• Electrical interference

from the spark plugs.

• Engine noise.

• Check or replace the

ground cable.

• Check or replace

spark plug wires.

• Check or replace the

noise capacitor.

Other electrical
components

-

• Noise may intensify

due to aging electrical
components.

• Repair or replace the

electrical components.

Static electricity (cracking,
crinkling)

• Noise disappears

when the vehicle is
completely stopped.

• Noise is severe when

the clutch is engaged.

• Noise occurs when

parts or wiring move
and contact vehicle
body.

• Return parts or wiring

to their proper
position.

Static electricity (cracking,
crinkling)

• Various noises are

produced depending
on the body part of the
vehicle.

• This may be due to

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

• Properly ground parts.

• Properly ground all

body parts.

AC204915AB

GROUND CABLE

ACX02360AB

GROUND CABLE