I got stuck again with a dead battery. Had alternator (3rd x) and battery replaced a month ago. When the gauge is hooked up at the battery, it shows not getting a charge. After reading some posts here , I wondered if the voltage regulator could be the problem. Where would this be located?
I would like to see if there is voltage going into and out of the regulator.

I have a 1984 Mercedes 300 SD Turbo.

Your vehicle may have an internal or external regulator. Both are easily replaced.
Click HERE for a visual reference.

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98 E300 DT
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86 Holden Jackaroo Turbo D
86 300SDL
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Thanks for the pics. Looks like it's an internal unit. Just can't imagine
what is wrong, since each new alternator would have a new regulator.



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1984 MB 300 SD Turbo

When you took the alternator back to the auto parts place and they tested it were the other 2 alternators no good?
From what I have read the charging "idiot light" bulb must be good and at least 2watts in order to start the initial current to the alternator if it is burned out or the wrong number of watts your alternator will not charge.

Pull out the alternator connector the one with the 3 slots. With the key off and the (+) probe (1 at a time and the (-) probe grounded) in each of the big slots you should read the same voltage as your battery(2 fat red wires). You should read no voltage in the 1 small slot (this goes to the charging indicator "idiot" light) skinny blue wire.
I have not tried this but when the key is on you should get slightly less than battery voltage from the small slot on the connector when the key is on. The voltage may show up as slightly less than battery voltage as the charging indicator light will use up some of the voltage.
If you are not getting battery voltage to the 2 big slots on the connector (key off) you have some problem with your wiring.
If you have no voltage comming from the small slot (key on) you indicator light may be burned out or you have a wiring problem.
The last problem can be the alternator is poorly grounded. Some member have taken a jumper cable connected to the (-) battery terminal and grounded it to the aluminum alternator body; if it starts charging after this it means your alternator is not grounded.

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84 300D, 82 Volvo 244Gl Diesel

Something to consider:

Is there a draw on the battery that you are unaware of??

Ie shorted wire etc


Have you tried jump starting the car and putting a VOLT METER across the battery terminal to see if the battery is charging?

Another way to see this is happening to start the car via jumping let it run for a while, shut it off, then try starting it agian.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

The point I'm trying to make is after a new alternator is installed, everything is great. Now today I shut car off and couldn't restart. Had to jump it. Took car to a garage, checked and was not charging. Can't figure out why it goes haywire.
Thanks for your help.

Not charging then you have a defective regulator or alternator

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Did you by any chance measure the battery voltage in your no start senario. Was it 12.5 volts or much less. As mentioned run a battery booster cable from the negative terminal to a good block or clean alternator area and see if it starts to charge. Three alternators is a little much.

I found this article while poking around the internet. Evidently some types of batteries need 13.8 or more volts or they will not charge. Here is the first sentence in the article:
"My Pantera has an Optima, which needs a charging voltage between 13.8V and 15V."
http://www.detomaso.nu/~thomast/alternator/

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84 300D, 82 Volvo 244Gl Diesel

Reach down with the engine off. Can you turn the alternator pulley with the alternator cooling fan blades? If so you have your problem. Do not feel bad if this is it. Many have precceded you. Only takes a second to check.

On my '82 300d the glow plug light stopped coming on, I had the battery checked, it was bad so I bought a new one. Still no GP light and the horn sounded like it was dying then the instrument panel lights went and now it doesn't start. Can anyone please tell me if this is the alternator or is it something else? Any and all help will be appreciated.

Thank you, 300dster

The alternator gremlens are back. The latest ( the old one was rebuilt locally because the NAPA replacement wouldn't even spin ) was installed last December. Today I stopped for fuel, wouldn't start. Not charging at all now. Alternator was spinning when tested.
Taking car to a shop that was recomended by two seperate garages. They are supposed to be very good at solving electrical problems. Hope they fix mine.

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1984 MB 300SD Turbo

Did you replace the battery? You may have a shorted cell, and so you show >12V when operating and all is well, but your alternator is working overtime to charge the battery and pour current into that short (creating heat).

A bad battery can do all sorts of terrible things.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)