Is this 993 fan and housing salvageable, and, why is my alternator throwing belts?

[Mixed76]

Hi all,

My alternator started burning and throwing belts, taking out the fan and ac belts each time. This is on a 1996 993 with 129k miles. Something would chirp on cold starts, but no issues with charging until the belt actually failed.

I eyeballed 1-2 mm of axial run-out at the blade tips when rotating the fan with belts off. One or two fan tips hit the housing lightly when the fan is spun by hand, but not if it is just rotated. Looks like maybe corrosion under the fan bearing insert has tilted the insert vs the fan.

Fan coating has cracked at the hub, more or less aligned with the run-out, and come away completely on the backside edge and elsewhere. Several blade tips and edges are blown open with corrosion. Clearly the fan tips have rubbed the housing.

The alternator shaft and pulleys have wear marks like the pulleys were sometimes rotating on the shaft. I can't figure how the fan hitting the housing would cause the alternator belt to burn up. I can maybe see the fan bouncing into the housing if the alternator was jerking around.

Alternator shaft has no visible run-out, turns smoothly but not as easily as I expected. Fan bearing turns smoothly and more easily than the alternator.

I'm thinking to rebuild the alternator and either have the fan rebuilt if that's possible, and if not, get a new one.

Thoughts?

Dan

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[john walker's workshop]

The fan is toast, typical mag rot. The housing might make it.

[Mixed76]

Thank you!

Pic of alternator shaft attached.

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[Trackrash]

I'd have the alternator rebuilt. It's already out and how many miles?

[KNS]

There's a service bulletin for an updated pulley on the 993. You may still have the older style though it may or may not be the cause of your belt issue.

[Mixed76]

Rebuilt the alternator (brushes and bearings), got a new fan with new bearing. Both alternator and fan spun freely on the bench, alternator sat in the housing but not screwed down. Now bolted to the housing with rear shroud in place, but no retaining strap, it lightly pings/ hits the housing with one or two blades.

It looks like the alternator is located in the housing by an inner ring matching up to a lip on the alternator case. That has light corrosion but no cracking, appears to be well aligned.

No issues observed at the bolt bosses.

If both housing and fan are magnesium it seems foolish to clearance either. Fan has a fairly thick coating on it as supplied from Porsche; housing is smooth dark gray, looks treated but not coated.

Thoughts?

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[Mixed76]

Attached and snugged up the strap, ping went away, mostly. Still no belts on, can get an occasional ping spinning by hand.

The new fan bearing seems awfully wobbly on the alternator shaft. The blade tips move > 1mm in/out - the whole fan and outer bearing race tilt - under light finger pressure. That's with all three socket screws snug, and the alternator pulley nut snug. Tilts in any direction, up, down, side to side.

Doesn't look like the inner bearing race is moving, only the outer. Anyone seen this before?

Send it back to Porsche?

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