Is it possible to replace the voltage regulator for one that puts out just a little more juice? I know the Porsche 944's are able to do this, to get their 12v up to about 13.8.

Has anyone done this? I'm not looking for something major that will burn up 32 year old wiring....just a little more would be great.

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI

Oh... -38 yesterday morning here...THAT'S why.

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI

I had an adjustable one, I recall it was a transpo, or something like that...
Had a screw to adjust the voltage.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

What do you expect to occur?

Are you trying to get your battery to charge faster, your lights to burn brighter, etc?

Put a multimeter on your alternator with the engine running. I would be incredibly surprised if your alternator is only putting out 12 volts. I would bet you are getting 13.5 to 14.5 volts of output.

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I don't know the same things that you don't know.

Shayne

85 W126 SD OM617.951
87 409D 650S OM617.913
93 E34 Touring M50B25TU
02 E46 Sport M54B30TU

If you're only getting 12 volts from the alternator something is wrong. Should be at least 13.x at 1500 rpm's.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The voltage put out by the various companies that makes Regulators for Bosch is hit or miss. You can only swap the Regulator and hope that particular Regulator pust out more Voltage. The below is sort of a general article on the regulators and there is a chart. But, I think that only applys to the individual Regulators that he tested.
http://www.humanspeakers.com/audi/alternator.htm

The article below assumes your Voltge Regulator is working but you want a higher Voltage.

This guy came up with a mod to increase the Voltage of his Regulator. One of our Members did the mod and it worked for him.
Bosch Alternator Regulator Modification with diode to increase resistance
http://www.detomaso.nu/~thomast/alternator/

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84 300D, 82 Volvo 244Gl Diesel

Diesel911, that sounds what I am looking for, so I'll check that out right away.

Guys, it's not putting out only 12v (I hope). In fact, it's probably not putting out much right now, as it keeps wearing the battery down after a few days of running to and fro from work (70km round trip). So I figured if I was going to try changing out the voltage regulator, then maybe I'd look at an upgrade as well.

As for what am I expecting? Just a little more charging power to the battery, as while I can have the engine preheated with the plug in, the battery take a you-know-what-kicking up here in the Great White North, especially this year.

Thanks for all the info guys, and add more if you got some.

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI

That link is dead, and while I can pull up the text in a Google cache of that page, the pictures aren't available.

But thanks, that put me on the right track.

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI

Here is the link to DieselGiant's DIY for a Voltage Regulator install.

http://www.dieselgiant.com/mercedesvoltageregulatorinstall.htm

Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

Thanks, much appreciated.

I have a Jetta TDI, a Dodge 3500, and a Porsche 944 that all seem to have battery draining problems, especially in the winter. The Porsche....well, that's probably the HID system that was installed. The Jetta and the Dodge....only in cold weather, so the diode upgrade might work for them too...wouldn't that be fantastic?

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI

On the Mercedes is your Battery Charging Light glowing red?

Some of the Members have said that when one of the Voltage Regulator Brushes gets too short sometimes the Alternator will not charge but the Battery Charging light will not glow Red like it is supposed to.

Also if your Battery Charging Light is burned out your Alternator will not charge. When you first turn your Key all of your Warning Lights should light up.

Remove the Electrical Connector from the Alternator. At the 2 large slots on the Connector you should get Battery Voltage all of the time.
At the single smaller slot in the Connector you should only get Voltage when the key is on (this is the one that goes to the Battery Charging Light, it has a skinny Blue Wire).

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84 300D, 82 Volvo 244Gl Diesel

The charging light works correctly when it is supposed to. The PO, if you believe this, was told that he needed a certain type of battery because if he didn't get the correct one "the car will kill the battery". One of the selling features for him seemed to be that it had the correct battery now.

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI

Battery flattens down after every few days use with a run like you have? Check for parasitic drain when the car is off.

Something does not sound right here unless you have additional loading from aftermarket stuff installed in the car.

Another thing would be to make up a harness from a cigarette lighter plug in to your voltmeter so you can monitor the alternators voltage out put to make sure it is not sagging down as the alternator warms up.

More important than anything perhaps is to reach down and see if you can turn the alternator by the cooling fins with the car off. You should not be able to of course. A slack belt or one under tensioned will quietly slip enough to reduce alternator output. About every few days what you say is happening would be understandable to me anyways. Minus 38 degrees is not.

If you have one of the 6 diodes blown in the alternator you will only get 2/3 of the power output just barely enough to run the car with no lights fans etc. The alternator will seem to charge a bit but not enough to stop the battery from slowly discharging. Take your alternator to a shop and have it tested. The diode trick will only work if your alternator , belts etc are good, but it will boost a good alternator up a half a volt or so if you need to. Be careful not to boil the battery with too high a voltage more than 14.8V is too much on a continous basis. Cheers Dan

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It's always something simple
91 300D 603.960 (from japan) 194K
92 Toyota Diesel Landcruiser HDJ81-t 116K
02 Golf TDI new head courtesy of PO
87 300D
97 BMW 525 TDS Wagon 5spd
bunch of Onan and other diesel generators