Mitsubishi 380. Manual — part 919

RADIO WITH CD PLAYER

CHASSIS ELECTRICAL

54A-210

INSPECTION PROCEDURE 10: 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
centre.

NO :

The observed noise is normal.

INSPECTION PROCEDURE 11: 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.

RADIO WITH CD PLAYER

CHASSIS ELECTRICAL

54A-211

INSPECTION PROCEDURE 12: Noise Appears During Vibration or Shocks.

DIAGNOSIS

STEP 1. Check the fit of antenna feeder cable.

Q: Is the antenna feeder cable fitted securely?

YES : Go to Step 2.
NO : Ensure that the antenna base and the radio and CD

player or radio, CD player and CD changer are fitted
securely. Check that there is no noise.

DESCRIPTION OF NOISE CONDITIONS

CAUSE

SOLUTION

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

• Increasing the engine

speed causes the
alternator 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 ageing
electrical components.

• Repair or replace the

electrical components.

Static electricity (cracking,
crinkling)

Noise disappears when
the vehicle is completely
stopped.

• 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.

16DB542A

NOISE CAPACITOR

RADIO WITH CD PLAYER

CHASSIS ELECTRICAL

54A-212

STEP 2. Check radio and CD player connector or radio, CD
player and CD changer connector C- 111 and C-117 for
loose, corroded or damaged terminals, or terminals
pushed back in the connector.

• Refer to circuit diagrams GROUP-

90

• Refer to configuration diagrams GROUP-

80

Q: Are radio and CD player connector or radio, CD player

and CD changer connector C- 111 and C-117 in good
condition?
YES : Go to Step 3.
NO : Repair or replace the component(s). Refer to GROUP

00E, Harness Connector Inspection

P.00E-2

. Check

that there is no noise.

STEP 3. Check that noise appears when the radio switch is
turned on while the vehicle is stopped and the radio is
tapped while tuned away from a station.

NOTE: Body static electricity from the shock absorber rubber
bushings used to prevent vibration, tyres, 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 and the radio is tapped
while tuned away from a station?
YES : Go to Step 4.
NO : It may be static electricity noise.

STEP 4. Verify that the radio is correctly grounded.

Q: Is the radio correctly grounded?

YES : Go to Step 5.
NO : Check that there is no noise.

54DB041A

HARNESS SIDE

3

9

4

12

14

6

13

5

1110

8

2

7

1

CONNECTOR: C-111

16DB530A

HARNESS SIDE

CONNECTOR: C-117

21

22

23

24

25

26

27

28

29

30

RADIO WITH CD PLAYER

CHASSIS ELECTRICAL

54A-213

STEP 5. Check by replacing radio and CD player or radio,
CD player and CD changer.

Q: Do the other radio and CD player or radio, CD player

and CD changer work normally?
YES : Either repair or replace the original radio and CD

player or radio, CD player and CD changer. Check
that there is no noise.

NO : Either repair or replace the antenna assembly. Check

that there is no noise.

INSPECTION PROCEDURE 13: Noise is Present While Moving (FM).

DIAGNOSIS

STEP 1. Check the radio after adjusting it.

Q: Readjust the radio. Is the noise eliminated?

YES : Check that there is no noise.
NO : Go to Step 2.

STEP 2. Check with several broad casting.

NOTE: Multipath noise and fading noise: Because of the fre-
quency of FM waves in extremely high, it is highly susceptible
to effects from geological formations and buildings. These
effects disrupt the broadcast signal and obstruct reception in
several ways.

.

• Multipath noise

This describes the echo that occurs when the broadcast
signal is reflected by a large obstruction and enters the
receiver with a slight time delay relative to the direct signal
(repetitious buzzing).

• Fading noise

This is a buzzing noise that occurs when the broadcast sig-
nal is disrupted by obstructing objects and the signal
strength fluctuates intricately within a narrow range.

Q: Is the problem station or location specific?

YES : The effect of an electrical field condition (multipath

noise, fading noise) could be the cause. Check that
there is not noise.

NO : Go to Step 3.