This means you need to swap the pulley and clutch. Very common issue when replacing Audi alternators with Reman'd or aftermarket units. You'll need special tools for this one, which ECSTuning carries.

 

I got a replacement alternator at Advance Auto Parts. $173 for a Valeo 120Amp Remanufactured. The 1st alternator had a short in it. This new one seems to be running fine and I'm getting about 14.5 Volts. Now, all that's left for me to do is figure out the heater issue (no heat) and get the LCD fixed (which is such an annoyance). With my wife being pregnant, I'll be driving her car so she can drive the X5 which is new. I don't want to have to worry about her getting stuck somewhere 8 months pregnant. But if this freakin car gets me stuck somewhere, I'm walking into a dealership and ordering a new car. We need more winter cars.

 

So does it have the correct pulley with clutch now?

 

Noooopee... The pulley was the same size... but w/o the clutch...

 

You need the clutch. It's there to prevent noise and prevent the belt from being thrown during sudden engine speed changes. Have the pulley with the clutch installed so your wife doesn't get stuck somewhere with a thrown belt.

 

Then how come Bentley and every other publication specs out BOTH clutch and non clutch pulleys? My mechanic and I really couldn't figure out why. The clutch would only freewheel if the alternator is spinning FASTER than the belt. With the pulley tensioner keeping the tension on the belt (and the tension is pretty strong), I'm having a hard time seeing the belt jump. And I'm having a hard time seeing the situation where the alternator would spin FASTER than the belt... Maybe you know why? Help!@?

 

If the engine was to suddenly decelerate, the belt would slow down significantly. In order to prevent slipping on the alternator's loaded pulley, it has a clutch. When the alternator is loaded (or fielded), it has a very high resistance. Trying to stop it suddenly results in a slipping belt. Any sudden changes like that not only can destroy the belt, but it can also prematurely destroy the alternator bearings. On the flip side, if your engine was to rapidly accelerate, the resistance of the alternator would rob power or spin up the alternator too fast and cause a voltage spike. With all the common alternator issues on A4's, you don't really want to mess around with it.

As a rule of thumb, if the original alternator had the external clutch, your new replacement should also have an exterior clutch, or at least have the original pulley and clutch swapped to it. IIRC, it only appeared on later models, so it might be VIN specific. I'd call Audi parts and give them your VIN. Ask them if you need the pulley with clutch. My guess is on yes, unless your rebuilt has a modified design with a built-in clutch.