Question about 3.2 Alternator Shaft

Laneco · 09-27-2010, 10:54 AM

I'm putting an 85 3.2 into my 81 coupe. This was a running engine. I took assorted bits off to replace gaskets, repair wires, painting, etc.

First off, the alternator/fan assembly came apart VERY hard. Normally a few well-placed wooden blocks and a thump or two seperates these for me, but this one was just beastly. In fact, I couldn't get it apart and had to have my husband do it.

Cleaned everything up and on assembly, the issue cropped up. The shaft on the alternator moves in and out about 1/8 to 3/16 of an inch. I can't really see any wobble in the shaft, but there may be some. I've probably fiddled with a half dozen 911 alternators, including another 3.2 and not seen this.

Under no conditions can I assemble the whole unit without this play evident even when the fan belt is on. Probably taken it apart 20 plus times no - no deal.

So...this isn't normal or a good thing is it? Need to replace alternator?

angela

Targa Me · Targa Me's Garage

without actually checking, i'm gonna say this is not normal. If no one chimes in by the end of the day, after work i'll go home and check, i have an alt sitting on the bench.
without looking i'd guess in your quest to remove the fan from the alt you inadvertantly displaced a bearing giving you the extra play.

AlfonsoR · 09-27-2010, 12:53 PM

Yeah, you have to be careful on removing the fan, take care not to apply impact loads on the alternator bearings (you say you used wooden blocks). I used a cheapo 2 leg puller. I had to grind a lot of material off the jaws so that they could slip into the holes on the front of the fan.

That said, I also messed around with my fan a lot a couple of months ago and can't remember the shaft moving axial at all, but I didn't measure that. I did measure the radial run out and I had about 0.005". I wish I had 0.003" or less.

So 1/8" is 0.125"!! That really sounds excessive.

gtc · gtc's Garage

Not normal, but it can probably be fixed easily with an inexpensive rebuild. It's when the shaft starts to wobble and your rotor starts rubbing the stator that you'll have a real problem.

Laneco · 09-27-2010, 02:03 PM

Okay, so really, this is a good news/bad news thing. The good news is that I'm going to get a rebuilt alternator! The bad news is that, indeed, this is our fault...

Well, maybe it was time to rebuild the alternator anyway.

I'm just disappointed because that means putting off installing this engine for a bit more. It looks soooo sexy - can't wait to drop the 3.0, wire up the motronic bits, and install this! And hey, guess I won't have to worry about the alternator for a while!

angela

Laneco · 10-29-2010, 08:31 PM

Thought I would follow up this thread and let you guys know what the outcome. I took the alternator to the rebuilder. Indeed, I had dislodged the bearing and that was the in/out play. But this actually burned out to be a "lucky" break.

The brushes were very worn, the bearings were just getting noisy and the regulator was flaky, voltage did not remain consistent. He said that the alternator would have failed very shortly even had I not dislodged the bearing.

I put the alternator back on today and everything went together perfectly the first time. No weird issues with the fan, etc.

So long and shot - you guys were right, and further probably kept me from being stranded somewhere in the not too distant future. Thank you.

angela

AlfonsoR · 10-29-2010, 08:52 PM

Thanks for posting the follow up. It's good to know we get em right once in a while. And for you...I bet it feels good knowing your alternator is purring like a fat, happy cat!! Good luck.

Walt Fricke · 10-29-2010, 09:11 PM

I like to use a chatter gun to get the fan off. An air chisel with a very blunt tipped tool in it. Press it against the end of the shaft while using your hand or something to apply outward pressure on the fan. Brrrrpppp. Usually comes right off. Doesn't seem to hurt the bearings.

Wil Ferch · 10:25 AM

Didn't read all the way thru....but note this--> thread pitch / diameter of alternator shaft for 81 may be different than for 3.2 or later 3.0's... don't know if this problem also plays out here, bit should be mentioned when mixing/matching parts.

3.2 ( and also "later"SC's with integrated Voltage regulator) ... M17 x 1.5

3.0 ( older versions....with external VR's)...... M16 x 1