I just figured I would post this in case anyone runs into the same issue. I have not heard it mentioned anywhere.

On my 1984 300D, I noticed in periods of extended idling (3-4+ minutes), the battery light on the dash would start pulsating. The car was otherwise driving fine. The one problem area was the cruise control would hunt a bit and was jerky.

I decided to investigate and noticed the alternator was producing as much as 16-17V. My voltage regulator was just over 2 years old and Hella (made in China). The brushes were worn a bit, but it should produce too low voltage when this part fails, right? Once the new Bosch regulator was installed, the blinking went away and now my cruise control is running perfectly.

I feel fortunate nothing got fried.

Dkr.

When the VR fails, the voltage will vary with engine rpm. I.e. it will be too low at idle, and then way too high when you rev the engine. This of course makes the electrical and electronic components unhappy. Glad you solved it before letting the smoke out of something expensive!

__________________
1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

I had the same problem. Swapped in a newer (not brand new), tested alternator into my w123 wagon. I had put a new (huco?) voltage regulator in the newer alternator - I noticed my lights pulsing just a little all the time. Voltage only pulsed from around 14v - 15+, but gave me the creeps.

Swapped in the voltage regulator from the old alternator into the newer alternator and it went away - so the new (but cheap) regulator was causing the problem.

Strange that the partstore test machine didn't show any problem.

__________________
1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI

My '93 Volvo 240 was doing the same thing, swapped out the VR for a Bosch and no problems since. Even scarier on a car with EFI... 18v voltage sparks can't play nice with the ECU/sensors lol.. on the plus side the car randomly got super bright lights over 50mph, I wonder what would've happened if I went 88!

__________________
04 Sprinter 3500 - 310k
"Ich mag die Dieselgeräusche"
https://youtu.be/YjrxHqNy5CQ
✞

Generally true for old electro-mechanical devices (ex. relays), but usually the opposite for transistors which generally fail short-circuited, i.e. "max output". An example is the transistorized blower-motor "resistor" pack (not resistors) in our 2002 T&C with automatic climate control. When it fails, the blower runs at max speed all the time.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans