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Discussion Starter #1
So, I bought an alternator about 13 months ago. I have a new battery. It seems like my battery is slowly draining. Was thinking it was the alternator. I tried testing it and alternator was charging a little, but not where it was supposed to be....
One question does the car still run if the car is on and you remove the battery? I was going to test it that way, however I know there are warning messages when trying to jump a car and such, so I didnt know if the car will yell at me.
Thanks
 

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Most cars up to 1993 then yes , car takes power to ignite from alt not from bat via VR . Newer model ECU need power supply to run the engine . Never try on my 02SA but only on my Cosworths . I could be wrong...:dunno::dunno:
 

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From Troubleshooters.com
"Your battery does more than just yield electricity. It also shorts AC, spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. The ECU, the speed sensitive steering, the memory seat adjustments, the cruise control, and even the car's stereo.

Even if your computers and stereo remain intact, in a great many cases removing the battery burns out the diodes in the alternator, necessitating a new alternator. If disconnecting the battery interferes with the voltage regulator's control voltage input, it's even possible for the alternator to put out hundreds of volts, frying everything.

Even the initial premise was wrong. If you disconnect the battery and the car conks out, you don't know if it conked out due to insufficient alternator current, or whether the resulting transients caused your ECU (the car's computer, which controls fuel mixture, timing, and much more) to spit out bad data, shutting down the car.

Nobody should EVER run your engine without a battery."
 

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Yes, Autozone will do the trick to test the alternator...

if the alternator is already out, replace the regulator, its fairly easy job, and costs 30 bucks...
 

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Discussion Starter #6
From Troubleshooters.com
"Your battery does more than just yield electricity. It also shorts AC, spikes and transients to ground. Removing the battery from the circuit allows those spikes and transients to travel around, endangering every semiconductor circuit in your car. The ECU, the speed sensitive steering, the memory seat adjustments, the cruise control, and even the car's stereo.

Even if your computers and stereo remain intact, in a great many cases removing the battery burns out the diodes in the alternator, necessitating a new alternator. If disconnecting the battery interferes with the voltage regulator's control voltage input, it's even possible for the alternator to put out hundreds of volts, frying everything.

Even the initial premise was wrong. If you disconnect the battery and the car conks out, you don't know if it conked out due to insufficient alternator current, or whether the resulting transients caused your ECU (the car's computer, which controls fuel mixture, timing, and much more) to spit out bad data, shutting down the car.

Nobody should EVER run your engine without a battery."
Thanks for that.. i havent done it because I was afraid that might happen.
I could do that with the 65 mustang.... but there are no electronics on that... so I was just double checking.
 

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Discussion Starter #7
Yes, Autozone will do the trick to test the alternator...

if the alternator is already out, replace the regulator, its fairly easy job, and costs 30 bucks...
Doesnt that require them to have the alternator out of the car? Sounds like a lot of work just to test.. was trying to find a simpler solution.

As i said before, the alternator is only about a year old... When I replaced it, I replaced the alt. and the regulator....

Couldnt find where to buy just the regulator... any suggestions? 30 bucks is definately cheaper
 

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Doesnt that require them to have the alternator out of the car? Sounds like a lot of work just to test.. was trying to find a simpler solution.

As i said before, the alternator is only about a year old... When I replaced it, I replaced the alt. and the regulator....

Couldnt find where to buy just the regulator... any suggestions? 30 bucks is definately cheaper
its a bosch regulator sold on ebay, as well as auto stores like advanced auto...

And the tester they have at these shops can check the voltage without removing the alternator....

one thing though, the charging current monitoring circuit built in the car is pretty advanced, it will turn a red light on in the dash if anything is wrong with the alternator...
 

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Discussion Starter #9
autozone can test the alternator without removing it? i thought it was a machine where u take the alternator out, adn they run it for you...
And i forgot to mention that.. when my alternator was bad last time... the light lit up... it is not this time... Good battery... was hoping good alternator?
 

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Discussion Starter #11 (Edited)
I went to autozone. Had a terrible experience. I asked them to test my alternator, and they went out to my car... First off THE STORE MANAGER was some young girl with long fake acryllic nails, poofy hair, and all dressed up as if it were a make up store. Normally appearance isnt a big deal, but when you know nothing about your job, it makes it that much worse. Second, when I showed her my battery, its clearly labeled positive and negative... she puts the negative on the positive and the positive on the negative... then when she finally gets it right on suprisingly only her second time, she says, this wont let me test the alternator...
After I was a bit irritated she then was like, well you can just buy another one...
ugh... no wonder why i never go to autozone...

As i said before there is no light on the dash saying its bad, and the battery is 2 weeks old, and the alternator is about 13 months old....
It was a hassle replacing the alternator... id prefer if I didnt have to remove it to test it.
 

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So, I bought an alternator about 13 months ago. I have a new battery. It seems like my battery is slowly draining. Was thinking it was the alternator. I tried testing it and alternator was charging a little, but not where it was supposed to be....
One question does the car still run if the car is on and you remove the battery? I was going to test it that way, however I know there are warning messages when trying to jump a car and such, so I didnt know if the car will yell at me.
Thanks
If your battery is slow draining, that is normal, as long as the drain is not too great.

Do not run the engine with out the battery.
It is going to cost you bid time.

Get a multimeter.

Resting volts depending of temperature, should be about 12.5 ( battery is good.)
Engine running less the 14.5 (alternator is working.)

The modules need 11 to 14 volts to be happy.

That's it.

Starting an engine takes about 375 amps for a V8 275 for a V6.

Your alternator will produce 100 amps when your rpm is about 3K.
If you don't use the car often, short trips, your battery will drain down.

Or if you have large amplifiers.........
Yes guilty I do.
That is why I also have a battery charger. ;)

Regards,
aam.
 

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So aam, what was the final outcome of your trouble with the alternator. I also am having the same symptoms and have replaced the alternator with a rebuilt one and it is not charging the battery. Showes less than 12 V back at the battery with a volt meter when engine running. 12.4 V at battery before starting. Idiot light on instrument cluster off with engine running. 500 sl 1990. Autozone said voltage regulator was out on original alternator, so ordered one off e bay changed out and reinstalled on car after autozone said it was good but it still didn't charge battery. I am getting darn tired of taking that alternator on and off if you know what I mean :) Any Suggestions?
 

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I never had a problem, knock on wood. Haha.

In your case I suspect that someplace a wire is lose.

So the alternator is not getting a signal or sometimes the wire strands are half broken.

Have a look in the module coffin, under a plastic cover are the main wire coming direct from the battery, then it splits, I also think that that's where the alternator feed is. ;)

How was the old regulator brushes?

You may got a defective wrong regulator.
Is it Bosch?
Get one from autohasaz use ONLY Bosch.
It is like $38

Regards,
aam.
 

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Thanks aam, I used a bosch regulator that came from a outfit in florida. VR on the original alternator was 1197 311035 and bosh replacement he sent was 1197 311027. He told me that they were the same. One was made in germany and the 027 was made in hungary. After I replaced VR autozone checked it while it was off the car and said it was good. Then after I put it on the car and checked voltage at the battery with the car running it was still below 12 volts, indicating it wasn't charging. So then I purchased a remanufactured alternator from Orielly's auto parts and installed it. Still not showing that is chargin back at the battery. Less than 12 V with the volt meter. I was going to try to trace down the wires from the alternator back to the battery to see if I might have a bad connection, but without any idea where they are run I suspect that will be fun. I am assuming that the small wire that is connected to the positive terminal clamp back at the battery is the wire that comes from the alternator and is supplying the charging current. Ill also have to look in the coffin as you suggest which is behind the fuse box in the back of the engine compartment drivers side.

Thanks for you response.......Bob
 

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The small wire located at the battery post, is supplying power to the rear fuses.

The heavy one goes DIRECT to the module coffin, LARGE main connector, there it splits to the main fuses, starter & alternator, it is located on the right engine side.
(Between the fire wall.)

It is important that the charge light bulb is not burned, as this excites the alternator.

Regards,
aam.
 

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The small wire located at the battery post, is supplying power to the rear fuses.

The heavy one goes DIRECT to the module coffin, LARGE main connector, there it splits to the main fuses, starter & alternator, it is located on the right engine side.
(Between the fire wall.)

It is important that the charge light bulb is not burned, as this excites the alternator.

Regards,
aam.
Found the spliter terminal block in the coffin on the right side ok. 12 volts on everything and down to the alternator with engine off. Charge light functions normal, on when key on engine not running and goes off after starting engine. Started engine and measured voltage right at back of alternator, large terminal, and still not charging. Showes around 12 V or below. Should be at least 13.5 to 14 volts. Off with the Orielly alternator and back to the store. Darn this is getting old. I also found the OVR relay and checked the 10 amp fuse, it was good, but still should have at least 14 or so directly on the back of the alternator. Will keep posting till the problem solved.

Thanks, Bob
 

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And something stupid.

Are you sure that the belt, and pulley and wires are tight?

Regards,
aam.
 

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And something stupid.

Are you sure that the belt, and pulley and wires are tight?

Regards,
aam.
Belt wires and pulley are all tight. checked engine to frame grounds, all ok. Alternator light in instrument cluster is performing as if alternator is good. Light on, key on engine off. Goes out when you start the engine just as if the alternator was charging, but I measured the voltage right on the back of the alternator, big terminal and engine ground. only around 12 v. Way shy of the 13.5 to 14 it should be.

Thanks, Bob
 

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something else stupid - did you check the alternator output with a different multimeter to make your meter is reading ok? i'm thinking the alternator could be charging ok and there's a partial short someplace which is draining the battery.
 
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