Alternator or pulley...help?

[bk.bas99]

Recently had a cambelt service, with new serpentine belt etc on my AWX 1.9TDi 2005 Passat, 130K miles Few thousand miles later and the alternator workshop! warning has come on and I am getting the red battery warning light. I have read lots about the pulley failing, but is there any way of categorically testing whether the pulley has failed or whether it is the alternator. I can get a reconditioned OEM alternator for about £80 or all of the bits to do the pulley (including tools) for about £50, but don't want all the headache of changing the pulley only to find alternator is shot. I only have a digital meter and battery is showing 12.5v but there is no increase in voltage when revving, so ccertainly looks like a charging issue. How to test please as don't want to drive car far if battery not charging!?

[zollaf]

pulley won't cause that fault, unless of course it has failed and is no longer turning the alternator at all, but thats unheard of. they fail locked so you get a jumping tensioner and some weird noises. sounds like you need a new alternator.

[bk.bas99]

yes pulley is definitely turning, just wasn't sure if clutch could fail in a free spin mode. There has been squealing on full lock which made me think of the pulley. Normally I would have jumped straight to the alternator with the no increase in volts fault but all the google hits say check pulley, especially with squealing

[zollaf]

aye, pulley will always turn, but is it turning the alternator. probably it is, but check first. sounds like you need both to be fair.

[micheal balbrig]

Something to check/eliminate is for a good connection where heavy cable connects to altenator

[stevegrass777]

The belt tensioner fails and that can make the belt squeel and alternater might be slipping also if the belt is to slack

[caldirun]

Recently had a cambelt service, with new serpentine belt etc on my AWX 1.9TDi 2005 Passat, 130K miles Few thousand miles later and the alternator workshop! warning has come on and I am getting the red battery warning light. I have read lots about the pulley failing, but is there any way of categorically testing whether the pulley has failed or whether it is the alternator. I can get a reconditioned OEM alternator for about £80 or all of the bits to do the pulley (including tools) for about £50, but don't want all the headache of changing the pulley only to find alternator is shot. I only have a digital meter and battery is showing 12.5v but there is no increase in voltage when revving, so ccertainly looks like a charging issue. How to test please as don't want to drive car far if battery not charging!?

Try turning the alternator internal fan with a plastic or wooden stick (chop sticks are good for this) the fan should turn one way only, if it does not turn in any direction the pulley one-way clutch is seized, this will trigger the Alternator Workshop warning. No alternator needed just a new pulley!

[bk.bas99]

checked the alternator pulley. It is not siezed BUT with the belt slack it does turn the alternator fan in both directions when I turn the pulley both directions, so is definitely not one direction only, buit as is def turning the alternator OK assume it is still the alternator not outputing. Brushes/slip rings/bearing?

[caldirun]

checked the alternator pulley. It is not siezed BUT with the belt slack it does turn the alternator fan in both directions when I turn the pulley both directions, so is definitely not one direction only, buit as is def turning the alternator OK assume it is still the alternator not outputing. Brushes/slip rings/bearing?

Do not slacken the belt, the idea is to turn the fan in one direction, the belt stops the pulley turning thus testing the one-way clutch, if the fan does not turn in one direction the pulley clutch is knackered.
This will give the warning you were getting, I had the same warning when my clutch seized, it seemed much worse at low revs (uneven running of the engine I would think)

[bk.bas99]

with the belt tight the fan will not spin in either direction, the pulley spins freely when the engine is running or when the belt is loose, but it turns the fan (armature) at the same speed as the pulley. I have removedf the alternator and ordered a reconditioned one from Schmitz as they recon OEM and the 120A Valeo for mine is a reasonable £80 delivered next day. By time I've bought pulley and tools I decided I might as well pay the extra £45 and get a fully reconditioned and guaranteed one. Will update thread once fitted!