Mitsubishi MOTORS Laser 1991, Service Manual, Page: 277 / 320

SYSTEM
Troubleshooting
Noise type
Sounds are in
parentheses
Conditions Cause
Inspection or replacement
Mounting place
preventive part (next
AM, FM: Ignition noise Increasing the engine Mainly due to the CRC filter
3
Snapping,
speed causing the
spark plugs.
Cracking, popping sound to Due to the engine
speed up, and noise.
volume decreases.
l Disappears when the Ground
2, 6
ignition switch is cable
turned to ACC.
AM, FM: Defogger
noise
It is generated when
the defogger switch is
turned on or off.
When the defogger
switch is turned on or
off, spark noise enters
the antenna. Noise
condenser
5
Other electrical
components Noise may appear as
electrical components
become older.
Repair or replace electrical
components.
Static electricity
[Cracking,
Disappears when the
Occurs when parts or Return parts or wiring to their
vehicle is completely
wiring move for some proper position.
stopped.
reason and contact
Severe when the
metal parts of the
clutch is engaged. body.
Various noise are Due to detachment Ground parts by bonding. Cases
produced depending
from the body of the where the problem is not
on the body part of front hood, bumpers,
eliminated by a single response
the vehicle. exhaust pipe and to one area are common, due to
muffler, suspension, several body parts being
etc.
imperfectly grounded.
failure due this may result in misdiagnosis due
NOTE
1. Condenser
The condenser does not pass D.C. current, but
as the number of waves increases when it passes
A.C. current, impedance (resistance against
decreases, and current flow is facilitated. A noise
suppressing condenser which takes advantage of
this property is inserted between the
line
for the noise source and the ground.
T h i s
suppresses noise by grounding the noise
component or pulse signal) to the body of
the vehicle.
2. Coil
The
coil passes D.C. current, but impedance rises
as the number of waves increases relative to the
A.C. 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.