alternator belt snapping
 

anyone any idea why my 964 keeps snapping alternator belts, on my third belt now in under 10k miles. its a 92 carrera 2 (tiptronic) and im lost as to why. anyone come across this before? everything seems to be lined up ok.

Is this in civilized street driving, or track (or even better: Isle of Man)?

I was breaking alternator belts on a dedicated track car, and have had no problem since going to a single pulley system (a la RS).

there was a TSB about that
New Alternator Pulley and Belt
©1998 Porsche Cars North America, Inc. Service Date: 2-5-98
Page 1 of 1
Binder - Service Technical Bulletins
This Bulletin replaces bulletin,
Group 1, # 7/97, dated 7-10-97

In case of alternator belt failure or belt noises in conjunction with pulley,
part number, 993 106 268 00 (s/s to 993 106 268 01), the alternator belt
and pulley must be replaced.
When repairs are necessary, install only the new version belt and pulley
halves.
Description Part Number
New belt (1 ea.) 999 192 372 50 (757 mm long)
Pulley halves (2 ea.) 993 106 268 01 (Yellow, chromated color) *
Shim (0.5 mm) 964 106 268 31 (as required)
Shim (0.7 mm) 964 106 268 32 (as required)
* The ratio of 2.68 to 1 remains unchanged.
911 Carrera:
The new version pulleys can also be installed on the 911 Carrera. However, the previous version belt
must be used.
Description Part Number
Previous belt (1 ea.) 999 192 343 50 (760 mm long)

no, the car is only driven on the road has never seen a track. single pulley system????

Sounds like the belt is the wrong one or being installed too tight. They will stretch a little but that should not be catered for at the time of fitting; it should be checked after 500 miles and retensioned if required. Where are you getting the belts from?

Can also be some damage to the lower pulley. The lower one on our 964 track/street car got damaged by gravel. Wife skipped through a gravel trap during a DE, picking up enough gravel in the tray under the pulley to damage the alternator outer lip. Have to look carefully to see it, but it's enough to cut up a new belt in 40 or so minutes of track driving.

Shims go on the inside AND outside of the pulley.

Digging up an old thread.

I'm in the process of installing my fan assembly after doing the single pulley conversion. The belt that I have is part number 999.192.338.50 and feels very tight. When I did a search to make sure it's the correct belt, google verified it.

Why are the part numbers in the previous posts different from the belt I have? Do I have the right one?