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634 Posts
Discussion Starter #1
I scanned through this forum and found bits of information, but would like clarification from the experts.

Using the diagram provided by ghnl in another thread, the alternator is attached to the engine with three bolts. Per this diagram:

  • Nuts (1) and (2) are 13mm and are easily accessible.
  • Bolt (3) has a 19mm nut on the bottom rear of the alternator, very close to the engine block.
Removal questions:
  1. Is there a recommended sequence to nut/bolt removal?
  2. Bolt (3)'s nut -- do I really need a cheater bar to loosen? Is this typical?
Installation questions:
  1. What is the recommended nut/bolt installation and tightening sequence?
  2. Recommended torque setting for nuts (1) & (2) and bolt (3)?
  3. Any other tips?


634 Posts
Discussion Starter #2 (Edited)
Alternator Removal

Today I removed the old alternator. Needed two 19mm sockets with 1/2" drive ratchets and a cheater bar for the 19mm nut on the rear of the alternator.

That 19mm nut on the back of the alternator was a nylon lock nut! Doubt that it was OEM, but it might make sense to use one.

Guidance for other amateurs like me:

  1. Remove bolt (3). The bolt will clear the fan for removal. Two 19mm sockets worked best for me. [Bolt size M12 - 1.5mm pitch x 115mm length with 92 mm shoulder. FYI Many hardware stores stock only M12 - 1.75mm pitch bolts and nuts.]
  2. Remove nut (2) and its corresponding bolt with two 13mm wrenches. [Replaced original bolt with new M8 - 1.25mm pitch x 25 mm length] [Original bolt size: M8, thread damaged by PO. Pitch was neither 1.0 nor 1.25 nor 5/16" SAE. Nut goes on far enough to get flush with end of bolt, but no farther. Hmm.]
  3. Loosen nut (1) while holding the alternator with your other hand. You can then position the alternator so as to slip off the belt and remove alternator.
  4. Remove cables from alternator.
It appears that my old alternator required an external voltage regulator based on the wiring connector on the back: D-, D+, DF. New alternator has an integrated voltage regulator with just a D+ connector. (Yes, both have B+!)

I am debating whether to just slide this connector onto the new alternator, using only its D+ female connector for attachment, or making a patch cable. More to follow.

634 Posts
Discussion Starter #3
Alternator Installation

Installed rebuilt alternator on Saturday and car is running great again. New alternator seems to have also eliminated some other, recent electrical gremlins that were affecting the dashboard.

Source for rebuilt Bosch alternator: bnrparts on eBay. Echoing comments from other board members in another thread: these guys are great. Good price, fast shipping, and they answer questions, even from amateurs like me.

Source for M12 - 1.50mm pitch nylon lock nut: Mr. Metric. I mentioned Mr. Metric before in another thread and now, after actually using them, can recommend them. Granted it's a short drive for me to do a will-call, but their no minimum order is a win. (I spent way too much time at Ace, OSH, and Home Depot, looking in vain for this lock nut.)

Diagnostic note: Definitely check the green wire connector that attaches to the alternator. A connector, or wire, failure could be the source of your problem.

Installation notes:
  • Install the M12 bolt with its nut loose. [Bolt (3) on illustration]
  • Install the M8 bolt with its nut loose. [Nut (2) on illustration]
  • Use the wood handle of a hammer to pull the alternator away from the engine block so as to get proper belt tension and simultaneously tighten the M8 bolt [Nut (2)]. (You can actually do this with just two hands!)
  • Tighten nut (1).
  • Re-check belt tension. If not good enough, loosen nuts (1) and (2), and then go back to the wood handle step above.
  • Attach red wire to alternator's B+ bolt.
  • Attach green wire to alternator's DF terminal. (You may need to install a new connector on the wire.)
  • Tighten the nut on the M12 bolt. [Bolt (3)]
I learned about the wood hammer technique at How a Car Works, which is an online reprint of a promotional book which went out of print years ago. The book is available online for free, but you can download it as a PDF for $5.
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