Proper voltage @ 38pin socket when engine is running --> does this affect communications with various modules?

[Jlaa]

What is the proper voltage output of the car when engine is running? Is it 14.0 volts? 13.7 volts? 13.4 volts?

I am troubleshooting a troubleshooting issue - I cannot fetch live data via my C4 from the EZL nor the DM when the engine is running, and the voltage at the 38 pin socket is 13.8v - 14.0v
However, I can fetch live data when the engine is off and the voltage is 12.3-12.4 volts. Notice the pictures below indicating voltage on my car.



Then I chatted with a German member of the German 500E Whatsapp group. He mentioned this to me:



This got me thinking about what is the proper voltage.... and then I found the below thread (highlights are mine) from some time ago pointing to a similar (but not exactly the same issue) wherein @carboRS2 was unable to get live data with the engine running due to having a way too high voltage output from the alternator?

ETA issues - Limp mode | Electrical, CAN and Wiring

I have recently rebuilt my engine and had it back in the car this summer. After re-connecting everything the car fired up and all seemed to be right but the ASR light in the dash. It's in limp home mode and can't solve it. First suspect was the ETA wiring because it was still the original...

www.500eboard.co

Thanks.

Hi everybody. I retake this thread.
During these months the car has been parked with the ETA not working.
Meanwhile I have purchased a Star C3.
When I run the test with just ignition it finds no errors. I can also read live data.
When I start the engine it can't connect with EFP module.
Is this normal?

No, that is not normal. You should be able to view live data with the engine running.

I have finally solved the problem.
I contacted Victor from restoreyourmercedes.com who advised me to check alternator voltage.
And he was right. The output voltage was 18v.

Hope this helps someone else in the future.

 

[JC220]

There are alot of variables to system voltage in any car

Battery condition
Alternator wear
Loadings / accessories in operation
Engine rpm
Etc etc

A healthy running voltage can therefore range from say 13.6 to 14 volts. In some cars with high output alternators up to 14.3volts is still normal.

 

[Jlaa]

Out of curiosity? What do you get at idle? I am getting 14.0 V at idle with no accessories turned on. I also get 13.8 V at idle with my HVAC on maximum high and all lighting including high beams turned on. The German guy tells me that I should be getting 13.4 V or maybe 13.7 V maximum in order to operate the C4 with live data from the EZL. I don’t know if that’s right or not right. Thanks.

 

[gsxr]

Just connected my C4 and saw 14.x volts with engine running and the C4 working perfectly. You DO NOT need a particular voltage for the system to work. I shot a video, trying to upload, stay tuned...

EDIT: The video recorded sideways! Aaaaargh. Rotating in the camera & re-saving only works when displaying on the camera, not in Windows or YouTube. Trying to figure out how fix it.... sigh...





Video uploaded & added below. I had to edit the movie with a Windows movie editor, which fixed the video, but screwed up the audio (sounds much worse than original). Gotta love Microsoft.

I measured 14.60 volts at cold start, using a Fluke meter at the battery, with a 150A alternator installed.
UPDATE 2: Same car, same meter, dropped to 14.00-14.05 volts when hot.