How do I know if alternator pulley is bad

jettajim

Veteran Member
Joined
May 31, 2000
Location
near Houston
TDI
'14 Golf 6-spd, '12 Passat gasser:(
Hi,

On my wife's '00 Jetta TDI with 174,000miles, I get the 'noise' everyone is talking about when the ac is on. Many people said it's the alt pulley.

Someone said to check the alt pulley, stick a screw driver in the vanes to prevent it from rotating in one direction. I did this and the pulley only rotates in one direction--as it should. Now, does this mean that the 'noise' I hear only when the ac is on and only sometimes, is caused by a bad ac clutch? When I turn off the ac, the noise goes away.

I changed the alternator about 40K miles ago with a reblt Bosch. The ac compressor was changed about 60k miles ago.

Thanks for your help!
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI, 2000 New Beetle
1) remove serpentine belt from alternator pulley
2) stick small screwdriver in the fan blades of alternator thru case holes
3) attempt to spin the pulley in both directions. Should freewheel in CCW rotation, lock up in CW rotation.
 

benIV

Veteran Member
Joined
Oct 25, 2009
Location
SE NC
TDI
Orville - 2003 platinum gray Jetta 5m 220K miles ||| Wilbur (Knurren) - 2003 silver Jetta wagon 5m 230K miles
Can you check it without pinning the alternator fan blades? eg. just spinning the pulley by hand both ways?
 

jettajim

Veteran Member
Joined
May 31, 2000
Location
near Houston
TDI
'14 Golf 6-spd, '12 Passat gasser:(
Thanks for the reply. I did that and it locks in one direction so does that mean the alt pulley is not the pulley making the noise?

Thanks again for your help.
 

benIV

Veteran Member
Joined
Oct 25, 2009
Location
SE NC
TDI
Orville - 2003 platinum gray Jetta 5m 220K miles ||| Wilbur (Knurren) - 2003 silver Jetta wagon 5m 230K miles
if it locks in only one direction (CW) and spins free in the other (CCW) then the clutch pulley is working properly.

did you check the alt. pulley or the ac pulley?
 

jettajim

Veteran Member
Joined
May 31, 2000
Location
near Houston
TDI
'14 Golf 6-spd, '12 Passat gasser:(
Thanks Ben.

The alt pulley locked in one direction when I inserted a screw driver into the blades of the alternator. It spun freely in the other direction. This is all with the belt off, of course.

I didn't check the ac pulley. How is this done? I read about people having the clutch come completely off.

Thanks again for the help!
 

benIV

Veteran Member
Joined
Oct 25, 2009
Location
SE NC
TDI
Orville - 2003 platinum gray Jetta 5m 220K miles ||| Wilbur (Knurren) - 2003 silver Jetta wagon 5m 230K miles
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