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Discussion Starter #1
ok..here goes.

2 weeks ago (as i submitted before) i was having battery issues. the battery got changed.

2 weeks ago i started getting this screeching sound from the speakers...which gradually increased in volume and intensity over a period of time. this would come whether the stereo was on or not. when the rpm's would increase, so would the screech volume....u could hear the sound of the signals in the speakers...

it got so bad over time that i think two of the speakers got a bit damaged. now, as they were 15 years old (or older)...i thought i'd get them changed anyway.

so today i installed new Infinity's in the front, doors, and rear. awesome. till we started the car.

and there was the screeching again.

now this is obviously some sort of short circuit or crisscrossed wires or something.

but any idea what or where?

secondly.

now...inspite of the new battery, the car almost dies when u turn on the a/c or headlights...or God forbid..both at the same time.

when u come to a stop...the car's rpm drops...and almost sputters...before recovering.

if u keep the car parked, and turn on any electrical item (a/c or lights etc), the rpm's drop drastically...and u can tell that full power is not available nor being supplied.

could this be the generator / alternator issue that was pointed out earlier?
 

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1987 420SEL
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If you have a volt meter check across the battery with the engine running. Should be about 14volts.
If no meter available, try disconnecting the battery while motor is running. If it dies it is a problem in the charging circuit. If it continues to run, start turning on electrical items and see if you can get it to stall. Stall, charging sys problem. No stall, charging is probably ok.
Beware of scrambling a factory radio (if you didn't when you changed the battery).
The noise in the speaker could be an indicator of the alternator going bad (worn brushes), also a reason for having to replace the battery.
 

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Discussion Starter #3
ok. will do this today. thanks.
 

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Discussion Starter #4
had the 'charging' checked today.

they put the voltmeter on the battery while the car was idling...and it was reading 12.40

when the a/c and lights were turned on...it dropped to under 12.

when the car was than put into gear it dropped to 11.5 or so.

so there's a definite issue with the alternator. going to have it opened up today and check the bushes etc etc.

the dealer said that this could quite possibly be the reason why i'm getting a screeching sound in the speakers...as the electrical system is getting insufficient power.
 

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93 190E 2.6; 82 300 SD Turbo
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also you might want to check the voltage regulator on the alternator, it could be that, its a cheaper part to replace than the alternator.

Good luck,
I had something simiar to this, turned out to be the battery...if your alternator is putting out the necessary voltage check for faulty grounds.

Cheers
 

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Discussion Starter #6
deathrattle - 5/4/2005 11:15 AM

mercbuff - 5/4/2005 8:02 AM

had the 'charging' checked today.

they put the voltmeter on the battery while the car was idling...and it was reading 12.40

when the a/c and lights were turned on...it dropped to under 12.

when the car was than put into gear it dropped to 11.5 or so.

so there's a definite issue with the alternator. going to have it opened up today and check the bushes etc etc.

the dealer said that this could quite possibly be the reason why i'm getting a screeching sound in the speakers...as the electrical system is getting insufficient power.

You shouldn't check the charging system with the engine only idling.It should be spinning at at least 1500 rpm or possibly higher still on an old car.If the dealer didn't even get this right,then i wouldn't trust his advice on anything else.Time to shop around,good luck!

[8D]
Thanks. the voltage (when the rpm was pushed to 3000) was still under 13.

i had my mechanic come in today and open up the alternator. turns out that 2 moving parts (forgot their names) are worn out. so they are producing 'power', but with much reduced efficiency.

they are being replaced...with a cost of about $140.

will update u again when the alternator is put back in tomorrow morning.

thanks for all the advice.
 

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1984 280SEL AMG
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It's the altanator. What's causing the sound out of your speakers is a set of bad diodes in the altanator. All altanators are A/C (Alternating current) The Diodes in the alt make the current D/C ( direct current ) when one or more of the diodes goes bad you start hearing the A/C current thrugh the speakers, If you had a small handheld radio and stood next to the car you can hear it thrugh that too.. The replacement altanator should fix all the problems.
If you wanted to be cheaper, you could replace the diodes and the regulator. Their are repair kits out there that come with replacement instructions ( how to guides )
 

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1988 560SEL sold:
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Discussion Starter #9
results

ok. had the alternator replaced today. got a 'hardly used' unit for $175. also had to change the belt, was cracked at one point.

cleaned the battery contacts....

result....13 volts at min and 14 at max!!!![:D]

the car is now no longer dying when it comes to stoplights, and i can turn on as many electrical gadgets as i want and it doesn't bat an eyelid.

now, what remained was the speaker crackling etc etc.

found out that the power wire that comes from the stereo to the battery, was loose. hence all the crackling etc.

now...no noise...no electrical problems....and the Infinity's sound great! (touch wood).

whew!
 

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Grats. Totaly awsome!!!
 
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