Replaced my '99 320 voltage regulator today with the help of a few threads on this forum. Had a slightly different experience than some of the folks in the other threads so thought I would share my experience in case it helps anyone out.
First of all, do what the kind folks here say and PULL THE ALTERNATOR OUT. I spent a lot of time on my back trying to avoid doing this and it resulted in me busting the plastic housing because there was a tab I couldn't see/get to. It doesn't take long to pull the alternator on a 320, so do yourself the favor
1) Unhook the battery
2) Jack up the passenger side, place jackstands and all the safety stuff
3) Pull the underpan - 8mm
4) Pull off the black cap and use a 13mm socket on the large wire connection
5) Use an 8mm socket on the smaller wire connection (other threads did not mention this connection)
6) Unlike the other threads, I was able to loosen the belt tension by putting a socket on the spindle in the center of the tensioner pulley (not on the nut) and turn counter-clock. I think I used an 8mm. Easily loosened up. Recommend pulling the belt off the top pulley first and then from around the alternator. Other threads mention using a 17mm socket on another bolt head but I could not find this on my car.
7) Remove alternator. I think I used a regular 11 or 12 mm socket here. Some WD40 and it worked fine. Move the hose out of the way and it should pull forward and up.
8) Remove plastic housing. Take out the 3 small screws and gently pull the 3 black tabs out to release housing. All of mine busted. Plus the crack I put in it trying to remove from underneath
9) Remove 2 screws that hold voltage regulator in.
10) Reverse. As another member here suggested, do yourself the favor of tapping the sleeves in the alternator mounts back out to ease you sliding the alternator back into place.
Hope this helps some future diy workers
First of all, do what the kind folks here say and PULL THE ALTERNATOR OUT. I spent a lot of time on my back trying to avoid doing this and it resulted in me busting the plastic housing because there was a tab I couldn't see/get to. It doesn't take long to pull the alternator on a 320, so do yourself the favor
1) Unhook the battery
2) Jack up the passenger side, place jackstands and all the safety stuff
3) Pull the underpan - 8mm
4) Pull off the black cap and use a 13mm socket on the large wire connection
5) Use an 8mm socket on the smaller wire connection (other threads did not mention this connection)
6) Unlike the other threads, I was able to loosen the belt tension by putting a socket on the spindle in the center of the tensioner pulley (not on the nut) and turn counter-clock. I think I used an 8mm. Easily loosened up. Recommend pulling the belt off the top pulley first and then from around the alternator. Other threads mention using a 17mm socket on another bolt head but I could not find this on my car.
7) Remove alternator. I think I used a regular 11 or 12 mm socket here. Some WD40 and it worked fine. Move the hose out of the way and it should pull forward and up.
8) Remove plastic housing. Take out the 3 small screws and gently pull the 3 black tabs out to release housing. All of mine busted. Plus the crack I put in it trying to remove from underneath
9) Remove 2 screws that hold voltage regulator in.
10) Reverse. As another member here suggested, do yourself the favor of tapping the sleeves in the alternator mounts back out to ease you sliding the alternator back into place.
Hope this helps some future diy workers
btw if your hands end up looking something like this you probably did it right 
I went one step further and stripped the voltage regulator down to add new brushes. You need to remove the black silicon over the brush end and hold the soldering iron on the terminals until the brushes are release. The file down your new brushes to suit the rectanglular hole and re-solder back in. Saves buying a new regulator !
