Over the weekend I started my 1982 240D, 157K miles, and I noticed that the starter turned the engine over at a slower rate. Today I got stranded in my 240D – no start, battery almost dead.
Jumped it, got it home and put a voltmeter across the battery while the car was running and saw only 11.4 volts.
My question: 11.4 volts is not good, correct. Does this necessarily mean the voltage regulator or should I look somewhere else before replacing the voltage regulator.
One more tidbit of information: I replaced the alternator in 2000 with 117K miles on the car.

Thanks very much,
Zill.

I would start with the regulator, as its the cheapest and least difficult possibility.

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1988 Toyota Camry Wagon......CRUSHED
1988 Porsche 944.......SOLD
1984 300SD.....SOLD
1995 Honda Civic DX... Totaled 11/13/08
1991 Madza Miata 193K and counting.....Mercedes t3 Turbocharger in the works 10 pounds per RWHP FTW

When you get a charging failure, and the red warning light does not illuminate, it's close to 100% it's the regulator.

Two bolts, and less than $40.

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

Jim,
The red warning light does not illuminate when I have the key in the on or 2 position. So that does point to the regulator, correct. Got the new one ordered, Thanks Phil. $33.00.
Thanks very much,
Zill.

The red warning light on the dash also acts as the excitation +12V feed to get the alternator alternating when it starts to turn. Unlike a generator, an alternator requires an external current source to start charging.

I've found that when the red light fails to illuminate when the key is turned to the number 2 position, the cause is an open in the regulator.

So, this sort of failure will not give you the telltale warning light. It's happened to me. Twice.

Jim

__________________
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