293 

 

No. 212 Large loudspeaker noise   

Malfunction Cause 

Solution 

Dirts in loudspeaker magnet 
clearance or cone diaphragm 
cracked. 

Check loudspeaker magnet clearance and cone 

①

diaphragm, 

whether there is dirt in the clearance or the diaphragm cracked. With 
that problems voice will be distortion when voice coil vibrating, and 
results raucity voice. 

Loudspeaker circuit poor contact 

C

②

heck loudspeaker circuit, whether it is damaged or short circuit 

to earth, as well as virtual connection between circuit and 
CD-player/loudspeaker. Maintain or replace it when necessary. 

Pull out the pins of CD

③

-player and loudspeaker, measure the 

resistance by multimeter, the value between both ends of circuit 
shall be 0 Ohm, the resistance to earth shall be infinite, and the 
resistance of loudspeaker shall be 4 Ohm. Inspect or replace when 
necessary. 

External appliances affection 

Check the appliances i

④

n engine cabin, high voltage wire for 

example, mainly inspect the electromagnetic frequency, generated 
when the appliances operating, which may affect the normal 
operation of CD-player and loudspeaker. 

CD –player stabilized voltage supply 
components malfunction 

Check the filter of CD

⑤

-player stabilized voltage, some may equips 

with inductive choke filter, then shall check current leakage in 
inductive choke. Replace CD-player when necessary. 

Check capacitor of circuit, whether it is damaged. Remove the 

⑥
capacitor and measure it by multimeter setting at voltage range, 
survey value variation between straight polarity and reverse polarity. 
If the variation range is too narrow, which indicates the capacitor is 
damaged, then replace CD-player. 

CD –player voice circuit short or 
damaged 

Most malfunctions 

⑦

in voice circuit appear on capacitor, cause 

current leakage or sealing-off always affect voice affection when 
playing, with load noise. Measure it by multimeter, replace 
CD-player or implement welding when necessary. 

Large 

loudspeaker 

noise 

CD –player power amplifying circuit 
short or damaged 

Check power 

⑧

amplifying circuit, measure the voltage between 

each pin by multimeter, survey the signal from front amplifying 
circuit, mainly inspect the capacitor, resistance, circuit and 
integrated package on circuit panel, whether there are evidences of 
burning. Replace CD-player when necessary. 

 

 
 

 

 

294 

 

Replace CD-player assembly 

CD –player power 
amplifiying circuit short or 
damaged 

CD –player voice short 

circuit  or damaged 

CD –player stabilized voltage supply 

components malfuction 

External appliances affection 

Loudspeaker circuit poor 

contact 

Dirts in loudspeaker magnet 

clearance or cone diaphragm 

cracked. 

Large loudspeaker noise 

Replace loudspeaker 

Maintain loudspeaker circuit 

Maintain modify replace 

Replace CD-player 

Replace CD-player 

Replace CD-player 

Normal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Normal 

Normal 

Normal 

Normal 

Normal 

 
 

 

 

295 

 

No. 213 Loudspeaker susurrates when pressing horn   

Malfunction Cause 

Solution 

Loudspeaker damaged or screws loose 

Check whether loudspeaker cone diaphragm is cracked. 

①
Check whether the loudspeaker retaining screws are loose. 
Since the vehicle horn mounting at front cross member, body 
will be vibrated when pressing horn, meanwhile, cracked 
diaphragm or loose screws will result CD-player loudspeaker 
voice distortion, as well as voice raucity when pressing horn. 
Solution: replace horn and tighten loudspeaker retaining screw.

Loudspeaker short circuit 

Check loudspeaker circuit, whether it is damaged or short 

②
circuit to earth, as well as short circuit between loudspeaker 
circuit and horn circuit. Measure the resistance between 
loudspeaker and earth, whether it is under normal range. 
Maintain or replace it when necessary. 

The screw of CD-player and horn earthlead 
loose 

Check the screws of CD

③

-player earth lead, horn earth lead 

and body connecting position, whether they are loose. When 
pressing horn, earth lead will be virtually conducted, because 
screws loose, the friction between body and earth lead will 
cause weak spark and generates interfering signal, which 
results loudspeaker raucity. Solution: Clean earth leads, and 
tighten the retaining screws. 

CD-player short circuit 

Check the resistance between terminal A3, at CD

④

-player pin, 

and body. Disconnect CD-player pin and rear view mirror pin, 
measure the resistance from A3 terminal to fuse by multimeter, 
the value shall be infinite, that is under non-conduction. 
Otherwise, shall maintain CD-player power supply circuit. 

When pressing horn, loudspeaker susurrates, then 

⑤

shall 

mainly inspect short circuit between horn circuit, earth lead 
connecting with CD-player earth lead, and CD-player circuit. 
Maintain circuit when necessary. 

Loudspeaker 

susurrates when 

pressing horn 

CD-player inner magnet interference may 
result loudspeaker noise 

Check CD

⑥

-player power supply circuit and inner stabilitized 

power supply, whether there is burnt or short circuit. Mainly 
inspect the capacitor between power supply and circuit, 
whether there is current leakage or damage. Maintain or 
replace it when necessary. 

Check anti

⑦

-interference or wireharness direction on 

CD-player. As well as screen condition of CD-player, whether it 
is interfered by screen wire damage. Maintain or replace it 
when necessary. 

Check CD

⑧

-player high frequency receiving circuit, whether 

there is damaged component, short circuit in circuit, or current 
leakage in high frequency capacitor. Maintain circuit or replace 
CD-player assembly when necessary. 

 

 
 

 

 

296 

 

Replace loudspeaker 

Loudspeaker damage or screws 

loose 

Loudspeaker susurrates 

when pressing horn 

Loudspeaker short circuit 

The screw of CD-player and horn 

earthlead loose 

Horn and CD-player short circuit 

CD-player inner short circuit or burnt 

Replace CD-player assembly 

Maintain and replace CD-player 

Maintain and replace 

Maintain and tighten 

Maintain, tighten and replace 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Normal 

Normal 

Normal 

Normal 

Normal