So decided to go grab some glue last night. Since it was a holiday I didn't drive anywhere so I started my car and let it warm up as usual but could smell something like burning plastic in my garage. Sniffed around further and it seemed as though it were coming from the passenger side and from the bottom of the car but towards the front. Did not see any smoke even after using my flashlight all over the engine bay.

Drove 2 miles down the street to lowe's as planned. Convinced the smell was not exhaust-related, I kept my OBD adapter plugged in during the drive to check for codes but nothing popped up. Got out the car at lowe's and could smell a hint of the burned smell. On the drive back, hooked up OBD adapter and did a few hard pulls from 0 to ~35 just to get the IAT's to creep up and check recovery (thinking maybe my pump or wiring is the cause) but IAT's recovered quickly so pump works.

Got home, parked in the garage and could pick up the smell a little bit. Finally brought up the voltage screen on the dash and bam, 11.6-7V readout as opposed to the usual 12.1 with the car off. "Well that's odd yet timely" I thought to myself since I have had the weirdest inclination to replace my main battery as preventative maintenance (planned on buying one this coming Friday). Started the car and the voltage stayed at 11.4V as opposed to usual 14.1V. So I popped the hood and took another sniff around SBC and the smell was there but faint.
Turned the key to position 1 and 2 with no change in smell.

Cranked up the car (which took a few seconds -which is unusual) and now the smell got stronger still from the area around SBC. Battery voltage gradually dropped and the convenience battery blah blah message popped up together with the red Brake error on the dash. Revved it to 800rpm and as the voltage climbs from 11.4 to 11.6 ish, messages went away. Finally after a minute or 2 of idling, convenience features message comes up and this time with Brake warning, ABS and ESP messages. Voltage readout was in the 10s now so safe to say I'm 4kd at this point.

Cut the car off and saw 9V on the dash. At this point I am guessing my alternator has failed or something inside of it. Picking up the new battery anyways at Advance tomorrow in the AM and either driving the car or towing it in to the dealership (14 miles away). I already have a couple of minor things I want warranty to replace anyway so timing isn't too bad.

Has anyone had such an encounter? I've read numerous posts from failed batteries to people replacing alternators to battery control modules. Where is the BCM located and to those that had failed alternators, what at all was involved and did any of you guys have any of these symptoms. All this happened just this past evening for me with no prior incidents.

 

my car just did this in december. Your going to need a new alternator. My alternator actually locked up and snapped the belt when it went bad.

 

Dam!! good luck with that mate!!

 

Have you looked at the thread by Loungn14 https://mbworld.org/forums/w211-amg/...lternator.html

May want to check that out first before spending the $ for a new alternator.

 

This exact post just happened to me a couple of days ago. I thought I could drive it a bit without the convenience features until I ordered the voltage regulator. My car is in a store parking lot as we speak (Sigh). VR ordered. I am hoping it is this and not the Alternator itself. I would order the Alternator now but would want to send it back if not needed (but not going to play that game). Hopefully, the DIY mentioned earlier will work out for me... We will see.

 

Is the alternator shaft moving freely ? Is the belt slipping ? Are you smelling a burnt belt ? Low voltage gives us a clue that it is either alternator, belt, or VR....

 

if you need ----> Voltage Regulator Replacement DIY- Its usually not the alternator

I have one really cheap. New In Box OEM

 

the VR is on sale at autohaus right now for 34 bucks Just ordered one...

 

Replaced mine under warranty a while back. No biggie.

 

same thing happened to my car, weird burned electronics smell under the hood. then my battery started dying. thought it was the battery at first, replaced it, same issue. voltage was showing 11.4 just like yours. now the car is at the dealership getting a new alternator under warranty.

 

That is interesting, hopefully you got this all sorted Yaw.

 

I notice that my dome lights start dimming, could the voltage regulatore be going bd?

 

I bought a Voltage Regulator ($49)hoping the cheap route would work. But I am not the lucky one today. The weird smell was the back of my alternator melting, where the voltage regulator is. So I get to pay $275 for a new Bosch Alternator and have my car down another week.

 

If you have a reputable local rebuilder, that might be an option

 

Please update with a final status when fixed. I suffered a similar smell, but have been able to delay fixing it for several months now. With the warmer weather, voltage is back up to normal so who knows whats going on.

best of luck