Alternator grounding strap?
Thread Starter
Junior Member
Joined: May 2016
Posts: 46
Likes: 3
From: Spangdahlem, Germany
2011 W221 S550 4MATIC, 2000 W202 C180 WAGON, 1998 W210 E240
Alternator grounding strap?
So I've gone through the ridiculous task of replacing the alternator on my 2011 S550 4MATIC. I know it's usually the voltage regulator, but I figured since my car has 105K on it it was probably better to just go ahead and replace the whole unit. I've got the car all buttoned back together and the car is still not registering the alternator. My problem here is that when I removed the alternator, I can't remember if the grounding strap was on the prong with the battery cable or if it was connected to one of the four bolts that hold the alternator to the block. 
Any gurus have the solution?
Any gurus have the solution?
Thread Starter
Junior Member
Joined: May 2016
Posts: 46
Likes: 3
From: Spangdahlem, Germany
2011 W221 S550 4MATIC, 2000 W202 C180 WAGON, 1998 W210 E240
I'm so happy you answered LOL. These are the directions I used during my removal. It was when I started going through the installation process that I noticed it doesn't mention the little 3-4 inch ground anywhere. 3 looks like it's the cable that runs to the positive terminal on the battery and 4 looks like the plug that clips onto the alternator. Is the ground supposed to be on there?
Thread Starter
Junior Member
Joined: May 2016
Posts: 46
Likes: 3
From: Spangdahlem, Germany
2011 W221 S550 4MATIC, 2000 W202 C180 WAGON, 1998 W210 E240
So, here's another one for the gurus. The prong on the back of our alternators is connected to the main lead (big wire) that goes to our battery distribution blocks. The alternator should ground its self to the block and with the little grounding strap connected to the frame. Does anyone know why my main lead wire would be reading as a ground (negative) opposed to a positive?
Thread Starter
Junior Member
Joined: May 2016
Posts: 46
Likes: 3
From: Spangdahlem, Germany
2011 W221 S550 4MATIC, 2000 W202 C180 WAGON, 1998 W210 E240
Bump.... why is my "large" alternator wire a ground? I have an 11 4MATIC and the pdf above has instructions that are a little different for my car. For example, my alternator HAD to be pulled out from the bottom. Impossible to come out from the top without removing the radiator. Second, the PDF doesn't mention the small grounding strap next to the alternator. Without it, the car won't even start so I know it has to be installed. I know our cars have an IBS, could that be the issue? Why would I be getting no power from the output stud on my alternator? And why is my large "B+ wire" a ground?
