How to Change the Alternator on a 1992 Mercedes Benz 300E

Removal
1. Disconnect the negative battery cable using the correct size wrench. It's usually 10 mm. Locate the alternator and disconnect the wiring harness attached to the back with a 10 mm wrench.
2. Loosen the pivot bolt connected to the alternator bracket. This will allow you to remove the Mercedes serpentine belt from the alternator pulley. If you are not replacing the serpentine belt, try to keep it aligned with the other pulleys. This will lessen the work of realigning it with the pulleys during re-installation.
3. Loosen and remove the bottom bolt attached through the alternator to the alternator bracket. This may be easier if you are under the vehicle. Remove the upper pivot bolt by sliding it out of the alternator bracket. Pull out the alternator.
Replacement
4. Slide the new alternator into place between the bracket. Push the upper pivot bolt through the bracket and alternator. Do not tighten. Slide the lower alternator bolt through the bracket and the alternator. Torque the bolt using your torque wrench to 15 foot-pounds.
5. Pull the upper alternator bolt out and slide the existing serpentine belt around the alternator pulley. Replace the upper alternator bolt. While pulling the alternator to the left to create tension in the belt, tighten the upper alternator bolt to 15 foot-pounds.
6. Reconnect the existing wring harness to the back of the alternator using the 10 mm wrench. Reconnect the negative battery cable using the same wrench.