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.