hi every one i hope you having good new year
i,m having problem with my alternator i don, knowwhate type of alternator was installed on my car the car working fine all day but when iuse it in the night it starts to drain the battery when i use the lights,defroster ,blower motor i checked the battery & alternator at kragen and they said it work fine under load the battery & alternator ok but i thing the alternator not giving enough amps to keep the battery in charge..
checked the alternator there is no sign of what type of alternator the only thing is the voltage regulator bosch p/n30062 on the back of it .any body know how to check the out put amps and any way that i can increase the output amps on those alternators .
thanks alot in advance..
300e 1989 plug in type alternator connector..

 

I had the same kind of problem on my 560SEL I replaced that regulator and everthing was fine. What I did to check the charging was hook up a volt meter to the battery and put it under load, lights, fan on high, and even turned the fog lights and found that I was only getting about 11.2 volts of charge at the battery. When I talked to a mechanic friend that regulator part was what needed replaced. I replaced it and everything has been fine since.

 

Good advice from jayhawkinIdaho. Battery voltage should be circa 14v under load (eg headlamps on and the engine at say 1500 revs). Anything less than 12.4 volts and the battery is bad (irreversible damage) plus possibly the alternator also which may have caused the battery to become seriously discharged.

The proper way to check the alternator is to connect an ammeter in SERIES with the battery but unless you are familiar with electrics this can lead to all sorts of hazards / risks which i wouldn't recommend.

Measuring the voltage (under load) is a quick way of getting an indication of what is going on.

Your local battery a/ alternator shop should be able to tell you what is wrong quickly and at a reasonable price but you may need to get two opinions since they want to sell you a new battery or alternator!!

 

hi
ok here is what ifound voltage output at idle is 13.7vdc with no load when iput load (low lights, blower,defroster,radio,) the voltage starts to drop until it reach 11.89 -12.00after about 8 minutsthats all at idle .when i rev to2000 rpm thevoltage gets up to 12.64 with full load..i took the car to two defferent kragen for free test both checked my alternator and battery and said charging ok ,battery ok.my question is how did the battery descharged if every thing ok ,is this type of car alternators manefactory 70 amp not good enough fo the car or who i bought the car from change a wrong alternator and battery .i can not till what amps on the alternator produce the only thing i see is the voltage regulator p/n 30 062 and i can not findn any place to verifiy the alternator p/n .is any way find the alternator amps by testing the out put amps i know the rated amps is not as the tested amps .

 

All your voltages are "about" 1 volt under what they should be.
A battery should NEVER go below 12.5v
12.64 volts at 2000rpm on load!
Something is wrong.
Of course it COULD BE your voltmeter?
How can the garage say all is correct if indeed your voltmeter is OK?
Question is whether it is the alternator (regulator) or battery since the two work in "tandem". The regulator receives its voltage control signal from the battery.
Unless you do lots of town driving the alternator should have sufficient capacity if it is working correctly.

How old is the battery? If its more than 3 years I would change the battery first. Basically it is a 50/50 call but batteries only last 3 to 4 years before they need to be replaced anyway. Then you will know for sure that it is NOT the battery.
I suspect it is more likely the voltrage regulator. These often give trouble.

Stuart

 

thank you for the reply snanceki
ok now i have been driving the car for aweek most of the time in aday light and the car voltage seems ok i,m still afraid to drive it on the night alot what i,m looking for now is a bigger alternator to install in the car .since i heard about 70 amps alternator is low for the car.
any way thanks alot for every one tray to help and i will post the change of the alternator procedure later on .

 

70 amp is low by todays standards but should be adequate UNLESS you do a lot of low speed town work at night.

110 or even 150 amps are now pretty common but this doesn't mean that you must have one. It all depends on what electrical load you have drawing power and whether you do a lot of load speed high power requirement stuff.

Good luck,
Stuart

 

hi
thank you for the replay
my concerns is the car will die on me again on the midle of the street .as i stated my alternator is new ,my battery is new ,no drain any where , no extra accessry added to the car. is the 70 amp alternator not enoughamps to cover the standard demand on the car .any way my plan is to find a bigger alternator to install in the car,
any one have done themodification tothe alternator to higher amps on the 300E 1989 engine type 12 173421 with plug in alternator connector

will be apprciated

 

hi every one
i just finished installation of the new alternator on my car the new one is 80 amps ,i had to removed my oldcable witchconnecting the alternator to battery and add some washers to align the pulley with the belt .
now i get 14.30 v at idle cold ,14.00at all speed with no load .with all load.the only thing is when i turn the rear defroster on the voltage drops to almost 11.99-1200voltwithout the rear defroster on the volt 13.59 all the time.

 

Hi,

So with the rear defrost ON and the engine revs at say 1500 - 2000RPM what voltage are you seeing at the battery terminals?
Above idle speed it should NOT be dropping to 12v!.

What do you mean you had to replace the alternator to battery cable? Why did you have to replace it?

Also what is the voltage at the alternator rather than at the battery terminals. maybe there is a big volt drop down the alternator to battery cable. there shouldn't be.

Stuart