Is this with or without the +0.5v correction?

96-97 E300 has an undersized 90a anternator that can barely keep up with the loads from afterlow, electric fan, electric everything. A lot of us have swapped 115/120/150a used alternators with OAP pulley off of other MB models. I would put a bigger alternator on it but the fact that your voltage drops as the car warms up and revs increase tells me your VR is on its way out.

I'll add my vote for voltage regulator.

Just went through similar behavior in my SDL which has a smaller alternator. With the original AVR I'd be somewhere around 13.5V unloaded, but only around 12.75V with accessories on at idle. Slowly the voltage would drop below 12V. Revving the engine >2K RPM would bring it back up ~13V but no higher.

Swapped out the AVR for a new one and I'm 13.2-13.8V at all times, regardless of load and engine RPM.

The AVR is ~$30, definitely the place to start.

x2, low voltage output especially on a car with 120k+ miles, I've found is usually worn out brushes. They get so low, they stop making good contact with the slip ring. For $30, it's not an expensive guess, and it's the most likely culprit.

I did not add the 0.5 volts.
The multimeter read 12.5.

What do you think about the WIDE OPEN THROTTLE ERROR CODE 462?

Its a non lethal trouble code - it turns off the compressor if you floor it supposedly to give you more power:D You have a non turbo 300 I think that is the least of your worries.

Thanks.
Does anyone know or think I can replace that Voltage regulator without removing the alternator?

If I have to remove it I'll probably pay a mechanic to do the job.

If not I'll go for it.

Thanks for all the help!!

If you can get under it you can do it without removing the alternator. Using the dental floss trick to set the brushes helps. Its about a 10 minute job once you are underneath.

It's much easier to replace the VR with the alternator out of the car. It's just 2 bolts to drop the alternator from underneath.

https://i.imgur.com/s5K4KqI_d.jpg?maxwidth=640&shape=thumb&fidelity=high

No idea on the W210, but I did it in my SDL without doing anything but crawling under the car. 2 Phillips head screws, old regulator out, new regulator in. Took longer to crawl under the car than it did to change the regulator out. Disconnect the battery first!

Agree 100% I can get under my SDL without jacking. With the 210's I need to lift. But its not easier to pull the alternator:cool:

I replaced the voltage regulator/brushes on my '97 E300D with the alternator still installed. I just drove it up on ramps and crawled under. The regulator comes out of the rear of the alternator. It has been awhile but I don't remember any problem.

Just saw this very good video on it.
Its done almost slow motion. And doesn't have some guy in a German lab coat giving me a 5 minute lecture in the beginning.

https://youtu.be/zVXL8IELiSw

I got in there. It was real easy.
Turns out I don't have the bosch alternator.
I have the Valeo.
Pelican parts doesnt even list this as an option. Rock auto does.... in fact its the only voltage regulator that comes up when you search my car. 1996 E300D non turbo.
Annoyed...
I found it at Hans Auto Parts for $5 plus 6 in shipping.
VW Part number
028903803F
VW
078903803A
VW
078903803B
VW

Ok.
So I got the right part from an alternator repair place nearby. Seemed like I'd get better quality than the $5 part.
I charged the battery and installed it and my readings 13.3 to 13.9 (12.8-13.3 before I add .5 v) depending On whether I'm Idling or driving.
This is basically the same reading as before.
So far the check engine light is still off after 20 minutes of running.
I also replaced the windshield washer fluid sensor. Which apparently is the reason I got instrument cluster failure warning.

Would a squeaky belt affect voltage?

Thanks for all the help on this guys.

The voltage seems to be the same as before I replaced the regulator/brushes.

BUT!!! I discovered that when I turn off all the fans and lights it sits at a solid 13.5 on the climate control readout. I think I had the fan running last time also.
Which begs the question....

Was there anything wrong with the voltage regulator in the first place?