Our new 140 amp Bosch alternator from Bavarian Autosport. Notice the difference in size compared to the original 80 amp alternator on the left. It's a direct replacement though... | 
Basic tools were needed for the swap. You could get away without the impact wrench, but you'll need a breaker bar to remove the pulley from your old alternator | 
Start by disconnecting the ground cable from your battery. Using your screwdriver and 8mm socket, remove the four bolts holding the radiator cover |
Remove the cooling fan. Using a slim 32mm open-end wrench, place it on the fan nut. If your wrench is too thick, remove the 10mm bolt before using the large wrench | 
The fan is reverse-threaded. Giving it a good, hard whack to the right should free it. This may take a couple of tries. Once loose, keep spinning it to the right until it frees itself | 
Pull the fan out. When finessing it around the upper radiator hose, you don't want to gouge the hose or the radiator. Also, a cold engine will keep that hose soft, making it easier to finagle the blades around it. Removing the radiator hose will make life easier |
If you've located the alternator and tensioner pulley, and can turn a wrench, you're qualified to complete the job. In the case of an E36 BMW 3-Series, the tensioner pulley should be lower left of the alternator and have a plastic cover on it. Pry off the cover with a screwdriver | 
Using an 8mm allen-head socket, turn the tensioner pulley about a quarter-turn to the right, as if to tighten it. This should loosen the tension in the accessory belt. While continuing to put pressure on the wrench, pull the belt off the alternator pulley. Take note of how the belt goes back on before doing this by either drawing a diagram or taking a photo, although there's really only one way it will go back on and stay tight... | 
The alternator is secured with two large bolts, the first holds the idle pulley. Take your 16mm socket and remove it. Removing the idle pulley and bolt completely will give you better access to the bottom alternator bolt |
Use your 16mm socket again to remove the bottom bolt so the alternator will be free to move | 
Before removing the alternator, disconnect the positive and negative wires from it. Rotate the alternator, locate the cover on the back and pull it | 
A 13mm socket will remove the nut holding the positive wire, while a 10mm socket will remove the ground wire. Your alternator can now be removed |
Since the new alternator doesn't include a pulley, swap it over using an impact wrench and 24mm socket. If you've got a strong friend to hog a breaker bar | 
After the install, we fired the ignition. We noticed the belt was off center around the idle pulley so we used a 1mm-thick crush washer on the upper alternator bolt to center the belt | 
The new alternator is a direct fit. Fitting is as easy as repeating the steps in reverse. Remember the cooling fan is a reverse-thread. Thread it to the left, free-spinning it until it stops. Once the engine starts it tightens itself... |