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Discussion Starter #1
I've got an 84 300dt sedan that's cooking batteries.

It wasn't charging the battery or powering the headlights until I replaced the Voltage reg some 3 months ago with http://img.eautopartscatalog.com/hires/W01331623408BOS.JPG?width=300&height=300 which I thought was the right one.

Now it evaporates all of the water out of my battery ( Search: H8-DLG | Battery | AutoZone.com ), which replaced with steam distilled about every 2 weeks for the past month and a half.

The car has a mystery year motor/tranny in it, from a donor 300cdt, I'm wondering did the voltages/amp req's change midway through the run of the w123? do i have the wrong battery/voltage regulator?

Thanks in advance for your help; I don't know jack about electrical issues.
 

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2001 Volvo V40
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2,954 Posts
The regulator wasn't changed. Have you measured voltage with the engine running. It should not be above 14.4 V, but it probably is.
 

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1984 300D
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If you are in the US Harbor Freight Stores sell inexpensive Volt/Ohm Meters (Multimeter).

The meter is also useful to check Glow Plugs.

It could just be the New regulator is faulty.
 

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99 SLK230 Kompressor, 5 Speed Manual
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1,117 Posts
Yes, you definitely need to measure the voltage. I have used low cost VR's on these cars with great success, but I don't recognize either of those brands as being one of them.
 

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Discussion Starter #6
Yeah I put the meter on it and it showed 14.0 volts at idle; who makes a better voltage reg than Bosch? Wasn't Bosch the OEM? I'm wondering now if the reg just isn't shutting off; continuously pumping juice whether the battery can take it or not.

This morning the car wouldn't even jump; but that could be related to the completely toasted battery wired in.
 

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99 SLK230 Kompressor, 5 Speed Manual
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1,117 Posts
Yeah I put the meter on it and it showed 14.0 volts at idle; who makes a better voltage reg than Bosch? Wasn't Bosch the OEM? I'm wondering now if the reg just isn't shutting off; continuously pumping juice whether the battery can take it or not.

This morning the car wouldn't even jump; but that could be related to the completely toasted battery wired in.
14Volts is not going to fry a battery. Even if it is fully charged and hammering 14Volts constantly, that should not fry it in short order. It will perhaps shorten the life, but I would not yet condemn that VR unless you have discovered something else that I did not pick up on when I read your post.
 

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Discussion Starter #9
well it's putting out 14v at idle. I haven't checked while the engine's above idle. I took compress ignite's advice and ordered a new voltage reg from peachparts and we'll see if they fixed it. If you remember from my first post i had a pic of the one that i ordered; peachparts lists that as a 'round body late style' vs. the 'square body, early turbo style' that i ordered (and was what I found on the alternator when i started this mess).

I assumed that a voltage reg for a 300dt was ubiquitous, but it seems that peachparts atleast makes a distinction. I'll install it when i get it and report back.

I'm also on the way to pick up a new battery.
 

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Discussion Starter #10
Final update, after some very trying parts sourcing from peachparts, I just bought a new alternator with internal voltage regulator installed. that and a new battery, and a few minutes to clean all of the connections and the car's been running like a champ.
 
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