Help needed with alternator-fan wobble issue
 

I rebuilt the old alternator when I restored the car/motor. When I installed the alternator it wouldn't work as the local shop who rebuilt it installed a voltage regulator with incorrect trigger amperage so it wouldn't work or charge... but that's another story.

I ended up having to use an alternator from a spare 3.2 as I knew it worked. This is an 87' 911.

Now that it's back in running I am seeing some wobble in the fan. I didn't notice it before, the new motor has about 180 miles on it and everything is working great. I noticed there was some dust where metal was being eaten behind the main nut. The nit didn't come loose but the 3 outside spacer shims (the extra's of the 6 in total, 3 being inside for belt tension) were being eaten up due to some sort of wobble or off balance issue.

Fan is brand new and so is shroud.

I took it all apart and you can see from the pictures below something doesn't like the way it's sitting. Once everything was off before I pulled the fan off I spun it and it isn't true. I'm unsure if there was a riveting issue when the fan was built/made or what but does anyone have an idea why this would be happening? I also spun the shaft by itself on the alternator (without the fan) and it appears to be straight. Guessing the fan could be the issue but not sure. As mentioned it was brand new.

PS. You can see in one of the photos where the outer belt pulley was being rounded out from it's initial rectangle shape to lock into that outer hub on fan...

Thank you for any help/guidance.

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On the last photo, that is the correct way that inside washer sits in there correct, the one behind the woodruff key?

I'm just taking a stab at this, but if you have wobble then I would think that the fan blades are rubbing somewhere against the fan housing when spinning due the tight tolerances - is there any sign of that on the inside of the housing? As to what would cause that, my first thought was the alternator - the bearings or the end cap being shot .. but you say that the alternator spins true with no movement ... which makes me wonder if there is a balance or off-center issue with your new fan ...

Is that the correct spacer in the last photo?

Jason

The fan hub is notched because the pulley was loose. Either replace the fan or have the hub welded up and reshaped as original, and get a new pulley half and 6 new shims. I see only 2 shims there, you need 6 total. That's the reason it's loose. Usually 2 between and 4 under the cupped washer.

It also looks like at least one of the shims got pinched, which could have led to the wear and the wobble. It can be tricky to get the outer shims to stay in place while you put the special washer with the tang on, and then the nut, all the while keeping the shims on the flats of the fan hub.

Some advocate using a bit of grease as a sort of low grade, temporary glue to keep these thin shims sitting right until the nut is tightened.

Agree with Walt, one (or more) shims dropped down and was pinched by the cup. And that outer pulley is rough, looks like the wrong holding tool was used and damaged it. Follow John's advice on the hub repair, get a new outer and a total of six shims (used to control belt tension) and re-assemble.

Fixed... fan was bent or had a wobble where the center section was riveted to the outer blade section. Pelican warrantied it and were all good now as I had a spare older fan in house.

Regarding the loosening. The belt only became loose once those shims (the weakest part of the system) started to deteriorate due to the wobble, they failed first... Once they failed the belt started to loosen which inherently made it worse.

Glad I figured it out. New fan on, straight and true and runs fantastic with no wobble or play in the shaft so glad it wasn't the alternator.

Thanks for all the input.

Video of fan running smooth and other goodies after restoration. Enjoy, I hope!!

https://youtu.be/VnwAwNrKKZY

good news.

I had an issue of "fan wobbling" once on a friends car as the casing of the rebuilt alternator was not properly tightened down all around (the 6 loooong bolts).
That lead to a misalignment of the shaft where the fan sat on.
took ages to find that one out...

Do I get a chicken dinner? :)

Glad u got it sorted out.

Jason