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drive: 1983 300D turbo ======== renovating: 1969 280 SE
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95 Posts
Discussion Starter #1
I just spend the past week trying to diagnose a problem and only today did I solve it after much hassle.

It started last Friday when I took a semi-long trip and started smelling rotten eggs/sulfur. I got home and checked here for anything like it and the word was that I had probably just bought some cheap diesel fuel and coincidentally, I had bought some fuel the previous Sunday from a station that you might suspect wouldn't sell the highest quality fuel and everything else matched..it was a warm day and it seemed to be coming from the engine compartment and something sounded like it was boiling or the like which I attributed to coolant in the lines. It got cool right after that and the smell went away until today.

Today, my car started smelling like that again(even worse) and when I parked it for a few minutes(after a very busy day driving), the starter slowly churned over enough to start again. I drove it to my house and turned it off to see if I needed to charge the battery and it started fine so I forgot about it but not for long. Two hours later it wouldn't turn over at all so I charge it up and get it checked out and that's when everything came together.

During the test/charge cycle they put it under, the battery started making that boiling noise I had heard...and soon afterward came the sulfur smell. Yes, it was indeed the battery making that smell. I had a slight suspicion that could be the case but with all the advice saying it was likely red dye diesel and me with little first hand experience with diesels other than big trucks at my father's shop over 20 years ago, I was inclined to go with the status quo.

This information did not come without a price, they said I need to check the alternator/regulator out because it might be overcharging the battery. I was in a hurry so I haven't yet gotten to check that but this is something to think about if that smell ever appears in your car.
 

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drive: 1983 300D turbo ======== renovating: 1969 280 SE
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95 Posts
Discussion Starter #2
Update: Getting 16-18 volts to the battery so it's easy to figure out that it's the voltage regulator.
 

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1978 280ce euro found dead on Ebay
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1,805 Posts
Carefull that rotten egg smell is hydrogen gas. Any spark near the battery will explode it. Then you will have battery acid everywhere. Don't smoke around the battery and remove negative cable first to avoid a spark. It best to turn car off and wait for a while before trying to remove battery.
 

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drive: 1983 300D turbo ======== renovating: 1969 280 SE
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95 Posts
Discussion Starter #4
Yeah, I know. Thankfully I'm a non-smoker cause the passenger compartment was completely full of the smell, and I assume the gas as well.
 

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1984 300D (311,500 miles)
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42 Posts
You know it's funny you mentioned this. We had the same problem with my wife's old 91 560 SEL and sure enough it was the battery and the highly explosive hydrogen and sulphur. Initially i asked her what had she been eating....lol she wasn't amused. Honestly be damn careful with a hot battery. Had one blow up point blank in my face years ago....glasses saved my eyes and a quick gallon of milk saved my head and face.
 

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21 Posts
Can anyone give a quick DIY guide on changing the voltage regulator?

Are these the same for all W123's or are they different according to your specific alternator?

Are they readily available - unfortunately my local Merc Dealer look at you as if you have just landed from Mars if you want to buy and fit parts yourself..........when for the 'competitive' rate £80 per hour labour cost they will gladly do it for you (not forgetting to add the V.A.T. of course)!
 

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2, 1985 300D Turbos, 1983 300TDT, 1983 SD
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122 Posts
Disconnect ground(negative) from battery.

Pop rectangular plug from back of alternator. There should be a small spring clip that you pry upward, that holds plug in. Two small screws, on left and right sides of regulator, that hold it in. Remove them and rock the regulator out, by tilting top out first, to make clearance for the brushes.

Reverse procedure by rocking brushes in first, and pushing top in while reinserting the screws. I've seen both slot and philips screws in them.

I've had a Napa regulator for almost 3 years. Lot cheaper than others. Of course, don't know if you have NAPA on that side of the pond.
 
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