VW Passat alternator belt just snapped for 2nd time
Discussion
There's 3 reasons why a serpentine belt would snap.
1) Wrong type or size fitted, or not aligned properly on the pulley grooves.
2) Seized tensioner pulley, but you would get an awful screeching racket to go with it.
3) Seized clutch in the alternator pulley, which is not obvious to most end users except when letting off the gas at high revs, but that's not applicable to diesels as they can't do revs :-)
The idea of the pulley clutch is to allow the alternator to 'free wheel' when the engine isn't accelerating. Modern alternators produce massive current and therefore need lots of (heavy) windings. These windings have substantial rotating mass which if not kept in check, can cause the belt to jump off, stretch, over heat, wear out.....etc.
It's easy to check. Relieve tension on the belt by putting a 15mm spanner on the belt tensioner and push it until the belt is loose. Now spin the alternator clockwise then quickly try and turn it counter-clockwise. You should feel the clutch free wheeling when counter clockwising it. If you feel the alternator turning in both directions, the pulley needs replacing.
1) Wrong type or size fitted, or not aligned properly on the pulley grooves.
2) Seized tensioner pulley, but you would get an awful screeching racket to go with it.
3) Seized clutch in the alternator pulley, which is not obvious to most end users except when letting off the gas at high revs, but that's not applicable to diesels as they can't do revs :-)
The idea of the pulley clutch is to allow the alternator to 'free wheel' when the engine isn't accelerating. Modern alternators produce massive current and therefore need lots of (heavy) windings. These windings have substantial rotating mass which if not kept in check, can cause the belt to jump off, stretch, over heat, wear out.....etc.
It's easy to check. Relieve tension on the belt by putting a 15mm spanner on the belt tensioner and push it until the belt is loose. Now spin the alternator clockwise then quickly try and turn it counter-clockwise. You should feel the clutch free wheeling when counter clockwising it. If you feel the alternator turning in both directions, the pulley needs replacing.
SuperchargedVR6 said:
The idea of the pulley clutch is to allow the alternator to 'free wheel' when the engine isn't accelerating. Modern alternators produce massive current and therefore need lots of (heavy) windings. These windings have substantial rotating mass which if not kept in check, can cause the belt to jump off, stretch, over heat, wear out.....etc.
Other way around, they disable the alternator under heavy acceleration to free up a couple of bhp when accelerating.They can also save emissions when it's not needed, e.g. battery >95%, low electrical load etc
annodomini2 said:
SuperchargedVR6 said:
The idea of the pulley clutch is to allow the alternator to 'free wheel' when the engine isn't accelerating. Modern alternators produce massive current and therefore need lots of (heavy) windings. These windings have substantial rotating mass which if not kept in check, can cause the belt to jump off, stretch, over heat, wear out.....etc.
Other way around, they disable the alternator under heavy acceleration to free up a couple of bhp when accelerating.They can also save emissions when it's not needed, e.g. battery >95%, low electrical load etc
SuperchargedVR6 said:
annodomini2 said:
SuperchargedVR6 said:
The idea of the pulley clutch is to allow the alternator to 'free wheel' when the engine isn't accelerating. Modern alternators produce massive current and therefore need lots of (heavy) windings. These windings have substantial rotating mass which if not kept in check, can cause the belt to jump off, stretch, over heat, wear out.....etc.
Other way around, they disable the alternator under heavy acceleration to free up a couple of bhp when accelerating.They can also save emissions when it's not needed, e.g. battery >95%, low electrical load etc
http://www.pistonheads.com/gassing/topic.asp?t=127...
Stand corrected
annodomini2 said:
SuperchargedVR6 said:
annodomini2 said:
SuperchargedVR6 said:
The idea of the pulley clutch is to allow the alternator to 'free wheel' when the engine isn't accelerating. Modern alternators produce massive current and therefore need lots of (heavy) windings. These windings have substantial rotating mass which if not kept in check, can cause the belt to jump off, stretch, over heat, wear out.....etc.
Other way around, they disable the alternator under heavy acceleration to free up a couple of bhp when accelerating.They can also save emissions when it's not needed, e.g. battery >95%, low electrical load etc
http://www.pistonheads.com/gassing/topic.asp?t=127...
Stand corrected
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