got a 01 996tt with 26k on it and a stick (apparently noting whether or not its a manual is important as they have two different alternators).
I ask because for the past several months my battery gauge on the dash sometimes drops to just over ten volts then the cars engine rpm will drop for a second and then levels off to normal (like when your a/c condenser kicks in) and the battery gauge returns to 14 volts.
I was thinking that possibly its the voltage regulator, but now not so sure as I mentioned that the voltage returns to normal when the engine feels like the ac condensor is kicking in even when it not on.
So I did a little research and turns out the manual transmission car alternators have a clutch that kicks in and out when necessary which is what I assume I am feeling when the voltage returns to normal. But my question is did my pulley fail which houses the clutch or is the voltage regulator going because it tells the clutch when to kick in or out?
I have no lights on the dash, the battery is brand new(didnt make a difference switching it out) and reving the engine in a stationary position does not make the lights brighter or make the gauge move.
Trying to avoid purchasing a new alternator so any help would be appreciated, thanks guys

 

I can't comment on the details of your post, but my alternator failed (voltage regulator) about six months ago. I had a local shop rebuild it for a reasonable rate. I can't remember the exact price, but it was definitely less than a reman alternator.

 

There is in fact a clutch but it is hard to say that your symptoms are related to a bad clutch or a bad regulator. But we see , especially lately, a lot of people with alterbator problems and often just replacing the voltage regulator fix the fault. It is cheap , I saw one at $13.85, but got one OEM for $40.00. Regulator part# F 00M 145 350 and the DIY is here: http://forums.pelicanparts.com/porsc...placement.html.

And here you will found someone who had problem with his clutch....https://www.6speedonline.com/forums/...e-reading.html

 

Thanks jp, it's the feeling of the clutch kicking in and the voltage returning to normal is just making me wonder if it's the clutch slipping or the voltage regulator not telling it when to kick in or out.
Curious if the clutch is just mechanical as spinning weights that at higher rpm it grabs or if it's electric like the ac condenser and receives a electric signal to engage.
Anybody know for sure?

 

From what I have read , the clutch is there to protect the Serpentine belt from harsh gear changes. It damps out the shock of the change and stops the belt getting too much strain.

If the Voltage reg is playing up the symptoms are normally fully charging when cold ( seems to be no problem) but as the car /alternator heat up the voltage drops even as low as 10v. It doesn't go back up again until the alternator cools down. ie when you manage to get the car started the next morning.

Frank

 

No there is not electrical connection to this clutch it is only mechanical not like the A/C. The part# of this clutch is 996 603 152 50 see pics....

 

Thanks for the info guys

 

Probably the regulator. You could replace it but you won't know until you reinstall the entire unit in the car and see if is charging. Maybe there's a test to identify a bad regulator but I don't know of one.

 

I am partially feeling towards the clutch pulley. Only because I have felt it kick in at a light and the voltage return to normal on many occasions and with it being mechanical and never getting any dash lights I think it's not a regulator issue. Also I have had the voltage low at cold startup as I hear regulators tend to fail at temp.
Plus I can remove it without pulling the alternator out of the car.

 

What you are feeling is the alternator load on the engine when it starts to charge and not the clutch. The clutch is a one way bearing. You can quickly test it by removing the serpentine belt and see if it free wheels in one direction and drives the alternator in the other. Your problem is most likely the regulator. This seems to be a frequent failure of even low mileage 996TT.

Andy

 

The clutch on the pulley is a weak point in the design of the stock alternator. I just replaced mine and went with a fixed pulley in order to circumvent this problem. If you decide to change out the alternator, might as well convert and not deal with this in the future.

 

Andy you are right about the test, I already tried it. I couldn't get it to fail but it doesn't always have low voltage all the time only once and a while and only for short bursts, that added to the ac condenser kick in feeling makes me think it's the pulley. As well as Porsche has updated the part to 997 part numbers. For $40 and not having to remove the alternator it's worth a shot. But who knows.
But a fixed pulley will cause unwanted wear and tear on other components with 6 speed cars and gear changes, (so I've heard)but I do agree it's a weak point.
Thanks for all the help and the insight