MB DOC, Steve B..2001 S430 complete electrical failure while driving
 

2001 S 430 110K miles. I was driving in dry weather and lost all electrical power. Dash went out, engine quit, no turn signals... Luckily I coasted to a safe place. When I put it in park I could no longer even turn the key. The key ceased to function re trunk unlocking/doors. I could see the light on the key blink when I pushed buttons on the key. When the flat bed came we put power to the battery and the car started. Battery is 6 months old. Tech is looking at it . Any ideas? UFOs?

Open circuit in battery?
 

Hi, The fact that the car started ok by just hooking a jumper battery to it makes me think that your battery failed. Although it's uncommon it seems like the only logical explanation. What did your tech say? Let us know.

Robert

'Open my Big fat mouth.
 

'Could your Alternator's Voltage Regulator's Brushes be Worn ????

(The fact that it died whilst running points to the Alternator)
[Yeah,and maybe the battery also]

But ,a VR is Much cheaper than a New Battery...

If the alternator had stopped putting out the battery warning light in the instrument cluster should have come on long before the battery lost all power. His tech is the one who is going to have to solve this mystery, but a good challenge is always fun and interesting. :)

Robert

Gremlins?

Tech is not sure
 

another fact that is important is that the dash went dark too. also no dome lights when the door was opened after stopping.
My dealer Tech is excellent.
He thinks the key could be the trouble as sometimes they go crazy but the loss of dash illumination is odd.
He said the ground to the battery was not super tight-not perfect but prob not the issue. Also alternator would provide some juice to the car under way.
There was no alternator light to come on. Sudden loss of all electrical capability in car.
He was going to plug in the laptop computer again this PM and rethink it.
In general I do not like electrical gremlins because they may return and make the car unreliable.
Thanks to all for trying. I was hoping someone would know about a harness recall like in the 90s or that it was an odd manifestation of the dashboard recall...

I had the same problem in my 85 500 SEL 7 years ago, all of the same symtoms. It was the altenator regulator/brushes has failed. Of note, the alternator light did not go on.

I also had an alternator brush problem in an 87 300E. It seemed different as the car ran on the battery until discharge. Battery ok in this case.

My w126 did the opposite.I was getting 18 volts,weakened the battery and lucky I checked and used all electrical stuff when driving,lights,fan,ect...

A odd but common problem on that model is a pin that falls off the EIS module - You mention the key quit operating trunk and doors and that's a big function of the EIS system to authorize operation.