1983 400i Automatic: Removal of Lower Alternator

Original 400 had a single alternator that was not sufficient at idle.

400 were later upgraded to dual alternator regardless of air conditioning. Late gen1 400i had the dual setup, not sure about early injected cars though.

The alternator are regular bosh units, except for the mounts, so although they are harder to find with the specific mount, they are just as easy to fix.

 

The fan belts can also make a snapping noise, quite common. Something to consider.

 

Immediately after I replaced all the belts I began to hear the snapping noise. It does it at start-up for a short while, then stops. Before I removed an alternator, I'd see if it is a belt(s).
If you do take the alternator out you should have a full set of new belts to install.

 

I'll second the comment about belts.
The snapping noise usually first appears when the belts are a couple of years old, and when the car has been sitting for a while ( the belts take a "set"). Goes away after a few minutes, no big deal, but sounds disturbing to the uninitiated.

 

Bret
If you are getting an alternator rebuilt, I suggest you upgrade its amp rating. The two alternators are rated at 45 Amps each. If you add the loads of: 2 fuel pumps, 3 radiator fans, 2 cabin fans (air or heat), headlights and wipers and you can get pretty close to 90 Amp load! I ran my battery down twice running at good speed but it was hot and rainy so I had everything on. A good Bosch rebuild shop can raise the amp rating to over 100 A. I raised one of mine (top) to 80 Amp as I was worried about overloading the little belt. It has worked fine. I have a thread posted from a year or so ago.
Ken

 

As long as the ammeter is not showing negative figures would not upgrade the alternators, as changing belts is a real pain. I'd rather change old fuel pumps in order to reclaim a few amps.

Upgrading the voltage regulator to higher voltage can compensate for the voltage loss, I would not go as high as 14.8v, but maybe 14.4v?

 

As far as higher amp alternator are concerned, a more aggressive winding makes the alternator react differently à cross the rpm range.

At idle a 100A winding will produce less amps than a 45A winding.

Below 2400 rpm (alternator rpm, not engine rpm) high amps alternators are not delivering any output so to say. I do not know what's the pulley ratio in our cars, so no idea of the actual alternator speed when the engine idles at 700rpm, but that's something to investigate prior to an upgrade project.

 

Yes, the upgraded alternator takes about 1000 Engine RPM to turn off the red light where the standard alternator goes out at 800 RPM or less.
Ken