Alternator Upgrade

[HB Chris]

What is the preferred alternator upgrade to get more amps? I see in a previous post that various e12, e21, e23 or e24 may work but at some point the bracket changes and I don't want to go that far, internal regulator would be fine, I will keep the external VR for appearance. Does anyone have the Bosch part number, the original was an AL45X I believe. Thanks in advance!

 

[velocewest]

Chris,
The internal regulator 65a from an e12 5er is a drop in. All you have to do is run the wire for the dash light from your old regulator to the D+ terminal on the new alternator. Generally these provide enough extra capacity to support upgraded lights, stereo, A/C, etc.

The e28 5er started with a 65a and by 1988 had an 80a or 90a alt (shared with the e30), but you will need to swap brackets for that. I think the very early e23's used the 65a like the e12, but most I've seen use a bigger alternator to support all the modcons, and those require the bracket swap.

If you don't mind working farther afield, pretty much any alternator is an option, within the limits of your patience for fabrication. I upgraded the 80a Marelli alternator in my Range Rover to a 120a Bosch from a VW VR6 application. All I had to do to fit that was to swap pulleys and trim about 0.5" off the pivot tube on the mount and use a shorter pivot bolt.

 

[jhjacobs]

I just around to installing an 80amp alternator to power my big driving lights (and get ride of my old externally regulated system. I picked up my unit from EagleKH (I can provide contact details to anyone interested) and he shipped quickly and offered assistance.

Anyway, the process was less than smooth. Here is what I found / did to get the job done:

1. The main pivot bushing ID is much smaller. I was able to use a smaller bolt. It also had a rubber bushing around the mount bushing. I used a smaller (13m Head) bolt / nut (with thread lock).

2. The tensioning bolt must be hair longer.

3. CRITICAL -The nut that holds the pulling on is recessed into the pulley on the original but on 80amp unit it protrudes about 0.4” from the pulling. This causes it to interfere with the power steering belt. This cost me many hours. First I tried longer belts to get the alternator to tension in a higher position out of the way (1” longer to too long). Finally had to shim the pulley halves to get the exact tension point.

The bottom line is that this is not a job for anyone without some patience. SHimming the pulley halves required an impact gun - I hope to never need to do this on the road!