I installed everything and when I finally tested, I had belt squeal at 2000 rpm. I know that there is slighly more energy required to turn this alternator than the old 90A, but when I started checking the tension on the belts, discovered that the belt and pulleys were greasy.

Long story short- make sure when you buy oil filter cartridges, you get the all the o-rings and the copper washer for your drain plug in the kit. Mine came without- so after 2 oil changes, the big oil filter housing/cover o-ring started leaking and got oil everywhere at highway speed. So, after driving to Chicago to get a filter kit (different car), I changed the oil, filter, and o-rings, then I removed the serpentine belt, cleaned all the pulleys, installed a new belt and etc. The reason I'm including this here, is that as long as you have the tensioner released and etc., now might be a good time to go ahead and change the belt anyway. If you plan for it before you start the job, you won't waste a day looking for a new belt like I did.

So- the new alternator is in, the grounds are all cleaned up, and the interior lighting is brighter than it has been since we've owned the car. The climate control is showing over 13v, and the multimeter is showing 13.5+ at the battery.

So does the 143A alternator from a 96 S420 fit in an E300 diesel? Yes, it do. If this has been of any help to anyone please post and let me know. Thanks, and thanks again to the others who posted info that helped with this project. Cheers! -J