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How to swap a 320i (e21) Alternator onto a non-tii BMW '02s

Written by Trent Tilton Friday, 30 September 2005 How to swap a 320i (e21) Alternator onto a non-tii BMW '02s How to swap a 320i (e21) Alternator onto a non-tii BMW '02s

By Trent Tilton

Parts Needed:

1977-79 320i Alternator. These can be bought new or found at the junkyard. You might want to get new alternator bushings at the same time. Most recommend urethane bushings as they will outlast the stock rubber ones by a considerable margin. Instructions:

  1. Disconnect Battery
  2. Remove stock 45 AMP Alternator - Remove 3 prong wiring harness and the 10mm bolt that holds the red wire. Remove bottom 13mm nut and bolt from the tensioning arm. Remove the top 13mm bolt. Remove Alternator, and list it on fleaBay (RARE! Original! BMW Alternator! ;)).
  3. Remove the square voltage regulator located next to the relays on the drive side engine compartment.
  4. The 320i alternator is internally regulated, so 2 wires only need to be hooked up. The wiring is very easy. The thick red wire goes back on the 320i alternator, on the "B+" post - this wire does the charging. Cut the BLUE wire off the stock 3 prong harness and connect it to the "D+" terminal on the alternator.
  5. Hook up the ground wire (brown) just like it was on your stock alternator
  6. Bolt up 320i alternator in the reverse of the removal procedure of the stock one.
  7. Tighten the fan belt just enough so that you can take the belt between the water pump pulley and the alternator pulley and twist it 180deg. Don't overtighten it because you will kill the water pump bearings. If it squeaks under load (when lights, etc., are on), snug it up a little more.
  8. Enjoy brighter lights and fewer charging problems! Take her for a night drive! :)

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(Cut the BLUE wire off the stock 3 prong harness and connect it to the "D+" terminal on the alternator.)

Hi, I have a 74 2002. When you say cut BLUE wire "D+" , is it from the alt side or regulator side? So if the regulator side is disconnected is the BLUE wire "D+" also connected to the charge bulb and ignition? Please advise.



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On 3/9/2018 at 10:00 PM, Hodgepodge said:

Hi,   Keep point missing.   Why would I want to do this?   Does this eliminate the need for a regulator?  

The main reason I'm switching to an internally regulated alternator, isn't for the extra amp juice (I really don't have a lot of extra electrical stuff slapped on my car) but because the replacement original type external regulators sold by Bosch, Beru,  and Hella, and others -  are often absolute JUNK....often failing days or weeks after installation. I had a battery BOIL on me during a 5 hour drive last year, due to a failing regulator. I'll be doing this swap today on my 69, hopefully.

Edited by wegweiser
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