Lots of good advice here.
I would probably buy a new battery and a set of jumper cables and/or one of those lithium jump starters (1000A at least)
Disconnect alternator.
Put new battery in.
Jump start engine from another car so that you don't draw down the battery.
Drive home, mostly in daylight if you can. Lights are a big draw, even if engine is not. Turn radio (and anything else that is power draw) off.
If you have to stop and turn engine off, try and jump start again (Lithium will help here if you are at fuel pumps)

By the way, voltage regulator is worth swapping. They are cheap and shops may stock them. If you remove the u-shaped air duct from air cleaner to turbo, you should be able to get at it. It the round device held on by two screws. It pushes into the back of the alternator (the rectangular device is noise suppressor, so not that).

Overheated boiled out battery may be toast. It may even have an internal short. If old one still holds charge after adding water (if that is possible), take it as a spare.

I understand your angst! We have a full house of relatives. Roof chose this time to develop a leak which dripped into our TV room. Luckily found a guy on Kijiji (like CL) who came on Sunday and patched roof (after scraping/brushing off snow). Two years ago, cast iron sewage pipes in our crawl space split open while we had a full house.

Not fun to have things go wrong when away from home and help may not be available.

Good luck, and enjoy your Christmas as best you can!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Something to think about when you disconnect the alternator, you need to remove and insulate all wires. Just unplugging the small wires might not stop the overcharging due to the regulator going full field. You need to remove the battery feed wire as well.

That Bosch type voltage regulator is used on lots of Euro cars so the chances of finding something is good.

Given you are in Columbus, perhaps DieselPaul could help. ( use the forum to send a e mail and PM )

I have bought new batteries with shorted cells,took back after one week.When they put the electrolite in sometimes they can't see the plates

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Only electrical connection is one large rubber enclosed plug. Just pulls out from back. By all means wrap some tape around it so contacts dont touch anything, but I think it is female plug, so not much chance really.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Wow, not fun .

A thought ~ ? are the headlights super bright ? if so the alternator may have failed a diode and be passing AC current to the battery, cooking it .

In any case, as mentioned you only need the electricity to start the car, once it's running you're good to go as long as daylight holds .

I've crossed America in oldies with fried generators and no parts, I just bought a $10 3 ampere battery charger @ Wallmart, ran all day and stopped as soon as the sun set, removed and charged the battery over night, walked to some local place to eat dinner and breakfast.....

This is do - able, don't panic, get home safely .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I didn’t mean any disrespect by that statement, just saying that it is possible to run these old cars on battery alone if you conserve your resources. I made the reference to Apollo 13 because they had a similar predicament, they had to shut off everything completely non essential for the return journey resulting in less than optimal conditions in the cabin yet they made it home safely.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

oh none taken, great analogy!

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1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

Thank you all SO much.

I was able to drive around (no alt, with a spare non-boiled battery i had in my trunk i forgot about) and i found an alternator on xmas eve.


I tried just doing the regulator but no such luck.


I really appreciate y'all taking the time to help.

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1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

Autozone and AAP do free alternator checks. IIRC, they have a bench tester, but also a connect while running type machine as well.

While you should have a multimeter (get one free at harbor freight if not; they’re as cheap as can be and lose calibration after a few years, but you’ll have a reading), get the test st the parts store. It will help you point out the issues.

As others have said, but I’ll reiterate:
- get water in there, or perhaps battery acid if you actually saw it leaking. Big difference between losing water due to electrolysis, and losing acid due to leakage. A quick search should find some. If you do this, charge the battery with a proper charger.
- if it’s the regulator, easy job to swap
- if more, you’ll need to be ready for a bigger job. You could DIY in a day if they can get the part, but can understand if not.
- look at the weather outlook, this will have a big effect on need for lights, wipers and ventilation.
- regardless I’d consider bringing a li-ion jumper, jumper cables, a spare group 49 battery, and tools.
- a voltmeter that plugs in the cigarette lighter is critical if you end up driving with alternator disconnected.

Good luck on this!!

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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)

Glad to hear you found an alternator. Hopefully it cured problem and you are set for trip home.

Did you find someone to install the alternator? I just did mine, but can't imagine having done it while away from home without proper tools.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I had to change an alternator in 'don't break down here, West By God TEXAS' and was able to use the open ended 17MM wrench from the factory tool kit to do the job, it was the first alternator I ever touched on a Diesel Mercedes, tricky until I realized the bolts were all on the back where I couldn't hardly see them .

I put the passenger wheels up on a curb in a passably clean parking lot and borrowed a sheet from a motel maid's cart (TIP: Motels & Hotels usually have clean working areas, you just need to remain to the rear of the property and work quickly) , was done ere long .

Now, onwards to the New Year ! .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Fun swapping them ain't it?...

Glad you got going, keep us posted if help is still needed.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

You can even get away with it to some extent on a gasser during the day.The charging light came on about 5 miles from my destination which was a lake in the desert (vehicle an Chevy Chevette). I kept going when I got to the destination I let it idle and had a 5 minute look and got back on the freeway.----------------When the battery got low enough what sounded like the seat belt alarm went off and I pulled into a gas station and had the do a quick charge on the battery while the engine was still running.--------------- I had to pull over one more time to get the battery re-charged when I started hearing the buzzer and was able to make it to a realities house that was closer then my home. It was over 100 miles from the Lake to the relatives house.---------------What made it possible was I guess I had a good battery to begin with. I stayed on the freeway as much and drove as fast as I could (did not have to sit idling or use up batter braking), traffic was not congested (Sunday), The Freeway was with in a mile of m relatives house so we did not spend much time in traffic, and of course it was during the day so no headlights needed.---------------This was before cell phones were common and had no Auto Club. I figured if it died at least if I got it closer to home and I could park legally I could get home on the bus and come beak another time to fix it.You also had to be willing to wait out the time about 30-45 minutes each for the batter to be recharged so that you had a good charge before you left.

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84 300D, 82 Volvo 244Gl Diesel

I learned a bit when I did my 300D. My 350SL has a similar system and I have had the alt in and out there, but somehow don't recall any problems.

On both of them, the adjuster rod and plate were distorted. Clearly someone (maybe me ) trying to adjust belt tension with bolts still tight.

What I learned:
- The bottom pivot bolt does not need to be loosened for adjusting belts. It doesn't clamp onto the alternator. Just provides a pivot.
- The nut for the bolt that passes through the top hole of the alternator is at back. It must be loosened to adjust belts. If tight, a wrench needs to be put on the bolt head at the front.
- The bolt that attaches the sheet metal bracket to the fixed alternator bracket on inner side near block, should be slackened off. Problem here for me, was that the nut is at front end, head at back. I had to get a wrench on both. Otherwise the bolt just spins. Doesn't need to be too loose for belt adjustment, just enough to allow bracket to pivot.

Found it easy enough to get at alternator and adjusters from top (after removing turbo inlet U-pipe). To remove alternator, not that hard to drop it out bottom after disconnecting bolts and electrical pug at top. It will rest on lower part of bracket while removing bottom pivot bolt.

I wouldn't have done this in our winter conditions without some encouragement from vwnate1

Hope to hear from lbjx2 when he gets back home!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5