Alternator Air Guide Part Numbers
 

Had a bit of an alternator rigmarole lately when a recently fitted (~3 month old) genuine Audi alternator failed suddenly.

I won't bore you all with the lengthy details except to explain that, due to Audi bureaucracy/procedures, a shortage of time and the difficulty in finding another alternator, I ended up with another brand new alternator (fitted) and my faulty (nearly new) alternator repaired (at my own expense, despite being under warranty still).

Interestingly (and perhaps the reason a new alternator at a reasonable price was so hard to find), any search for the original alternator part number (077903015P) returns results for Lamborghini Gallardo alternators, which seem to sell for silly money on Ebay.

So, getting back to the alternator air guide ...

I'm not sure how important the air guide is but presently it isn't fitted. Despite having the correct part number, the new alternator has a slightly different design, with the air intake entering from below instead of the side, and there's no way to rotate it.

Looking at the parts catalogue, it seems there were two different designs of air guides, one of which appears to attach to the bottom of the alternator. However there seems to be no part numbers listed for these (on the online catalogue at least). Does anyone here have the part numbers?

Link to the relevant page is here: http://www.realoem.me/Audi/RDW/A8Q/2.../903/903080#21

It looks like I need parts numbered 20 - 23 here:

http://forum.a8parts.co.uk/attachmen...1&d=1532010178

Now that is interesting. The one I'm working on at the moment has the inlet pointing down as well. I assumed it was an aftermarket unit that was just assembled incorrectly.

I'll have a look for numbers...

What you have there is the 150A alternator for the V6 engine.

The items in your diagram don't show up for the D2, only for the C5 A6 V8. Checking the part number for the 150A A6 V8 alternator (038 903 018D), it cross references to the D2 V6, which normally has a 120A. The 150A version must have been fitted to the V6 as an option, and it seems someone has mistaken it for the 150A V8 version which is 038 903 018G.

In theory then, the air guide for the 150A V6 D2 should work. That is 4D0 903 423B for item 20, and 4D0 903 655 for item 21 & 22 combined. I've got a couple of V6s at the workshop so I might have a look later if I get a chance +++

Brilliant, that explains a lot!

Thanks muchly MJ +++

How important is the air guide? And what does it connect to?

I do not have it on my car. And the plastic cover on the alternator is broken.

I'm not sure it does much at all. I've driven without it connected for weeks with no ill effects.

It just seems to duct air from the front grille, so any cooling effect will be greatly dependant on the speed of travel. Considering that the power demand on the alternator is not necessarily speed dependant, I would imagine there are often times when there is no airflow but the alternator is working hard.

In the diagram, part #6 (or #20) sits just behind the grille.

I see. It looks like the airflow is going through the alternator from the rear to the front. Without it, I guess the only airflow would be in the opposite direction.

Anyone wondering how to spot the difference, here's the V6 version (on the left) compared to the V8 version (on the right)