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Alternator Swap

The car has always seemed to have low voltage since I own it as you can see in this photo

After  reading about people who swapped Volvo alternators I decided to look for a possible Mercedes replacement unit.  The one I selected (because it was given to me) was removed from a 1990 Mercedes-Benz 300TE 4matic and rated at 80 AMP vs. the 50 AMP unit installed at the factory.

Before beginning the swap I had the donor unit tested at a local auto parts store, it passed!  To be safe I elected to replace the regulator & brushes before installing it on the car.

In the below picture the old
regulator & brushes are at the top and the new regulator & brushes are shown at the bottom.

Both being Bosch / Mercedes units the cases were the same size and bolt pattern - in fact even the pulley was the sameUPDATE: Although not noticeable with your eye, the new pulley was a smaller diameter.  I went back later and swapped them to ensure there would be no issues with drive belt length or tension. 

One change I did need to make to the donor unit was rotate
the two halves of the case by 90 degrees so that the connection point for the wires allowed proper routing of the wires.

 <--- Factory position

 <--- Rotated Position

That's it for the factory part's, time for the fabrication work to begin.  The factory wiring for the 50 AMP alternator is very light gauge wire.  In fact so light I decided to upgrade the alternator harness with a homemade harness comprised of dual 4 gauge wires.  It might be a bit overkill, but it won't be the cause of low voltage or fires.  The second reason for a new harness was because the old unit used a connector that was incompatible with the new unit.  The final reason is that since I haven't molested the original harness I can easily return to the factory setup if ever required.

  <--- Original Wiring

  <--- New Wiring

  <-- Old & New Wiring Harnesses

I reused the heat shield to route my new harness then I added split loom tubing to protect the new wires in exposed areas.

My total investment was $50, two trips to the auto parts store and six hours in the garage.

Additional photos of the install are available here.