GM Alternator

It’s been said that is is better to have it and not need it than need it and not have it. I was planning to add some electric loads to the BMW (EFI, Fan, AC, Stereo, etc) and figured that philosophy could easily be applied to alternators. The 2002 came stock with a 45 amp alternator. Based on a quick estimate of loads (not all on at once, I determined that an alternator of at least 80A would be safe.

HVAC blower10
Electric Fan10
Misc (Radio, Lamps)15
Electric Fuel Pump10
Power Windows10
Load estimate for alternator capacity

Potential swaps in the BMW family (AL41x, AL44x and AL46x) from later models did not quite meet my needs (power, cost, availability). A popular hot rod solution is a GM “one wire” or similar internally regulated alternator. They have an internal voltage regulator, are available at higher outputs and are widely available. I picked up a 105A alternator at the local pick-a-part for $35.

To mount it, I used the stock upper mount with some spacers and an E30 adjustable mount. The bottom bar is pinned to prevent it from rotating.

Wiring was accomplished with reference to Zeebuck’s site and the following alternator wiring diagram.

Posted in: BMW