[Vwdiesel] Free wheeling alt pulley WasRe: Re undersized pulleys-1.5 engine

Sandy Cameron scameron at storm.ca
Thu Aug 28 12:42:13 PDT 2008

At 01:56 PM 28/08/2008 -0500, you wrote:
>As far as pulleys and alternators are concerned, my 04 Jetta TDI actually 
>has a pulley on the Alternator that freewheels at certain speeds thereby 
>reducing the load on the engine.  I guess since there is minimal electrical 
>usage on diesels they decided to save a bit.  Hayden

No, it doesn't freewheel at certain speeds, it is an overrunning clutch that
allows the alternator to overrun and slow down slower than the engine when
decelerating suddenly, (like on rapid up shifts).

This reduces serpentine belt whip, caused by the rotating mass inertia of
the alternator and came about because of early tensioner bushing wear-out,
and also might have had something to do with the crankshaft nose failure on
early 1.9s.

It became standard equipment on the TDIs. I have retrofitted one on my 94 TD


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