Alternator specs

[62willys]

Just want to start a thread to hash out the differences in alternators between the v6 vag engines. There isn't that much info out there and as my alternator just quit in my 2.7t allroad, it's like pulling teeth, trying to make sense of my options.

With respect to the allroad, their were 120 and 140 amp alternators fitted. There were also 2 manufacturers of each; Bosch and Valeo. Apparently the brands aren't interchangeable but if you stay within brand (Bosch for Bosch, Valeo for Veleo), you can upgrade to the 140 amp.
That said, what I've gleaned from researching is that the relationship between pulley centerline and the mounting surface of the alternator is the same, however, the relationship between the face of the alternator and the pulley centerline are not. They will not, however swap pulleys between the 2 brands (you can't put a Bosch pulley on a Valeo alternator or vise versa). Someone please correct me here if I'm wrong.
So as long as your alternator comes with a new pulley, the 2 brands should interchange as well.

I've also come across some unverified evidence that any alternator from a 2.7t, 2.8, or 3.0 (circa C5) will work, I believe even from a B5 chassis 2.8.
I've come to this conclusion by researching part numbers of applicable alternators and cross referencing them with parts houses and manufacturers databases.
This would be good news as it opens up more options for us when it time for a replacement. It's even better news for us allroad owners whose compressor add substantially to electrical demand. 140 amp is good but 150 or 160 amp adds that much more room. After all, any component that's run at or close to its limit will fail sooner. And since an alternator will only produce what's required of it, there's no risk of overpowering, only under powering.

Any thoughts , recommendations, rebuttals, or advice? Post em up.

[Audibot]

Subscribing to hear what smart people have to say.

[62willys]

Thought I would add:
Manufacturers use similar cast bodies for their alternators. A 160 amp alternator will (may) require a slightly larger body to house the additional windings than a 90 amp. That said, they are driven by profit and new castings and tooling will eat into the bottom line. More often, it seems they engineer a solution to meet the manufacturers design specs with respect to size and output, using resources they already have.
I will say that although this is the case, they also make many housings for the same "guts". The armature, windings, diode pack, slip ring, and regulator are all similar within an output range (say 90 amps). They may differ based on cw or ccw rotation to some respect but a 90 amp "package" is what it is, the guts. So the housing mounting requirements are the biggest wildcard (for manufacturers and us) there are 2 ears when looking at an alternator straight on at the pulley. The pivot ear is cast at the 6 o'clock position (manufacturers use this to locate the parts and ears around the circumference). The pivot ear is usually doubled (one behind it as well). The other ear can be anywhere else around the "clock". Some are mounted totally differently but for our purposes that and therefore they are irrelevant. The same goes for water cooled alternators, et al. Interesting but pointless for our purposes.

So the reality is that an alternator is basically a closed system. It only interfaces with the rest of the vehicle in a few ways; the centerline of the pulley, the mounting surface of the ears and the relationship between those two things. The minutiae of it is making sure the exciter wire connector will work and your power lead to + will reach and is of sufficient gauge to carry the amps your alternator can produce.
So finding an alternator whose cast frame has matching ears (remember the clock) to ours and fits in the space allocated, is a good start. Since the mount for our alternator is shared with a number of other engines, any alternator body that attaches to this mount on another vehicle will also attach to ours.
From there it's a matter of having the proper pulley and making sure the distance between its centerline and the mounting surface is the same as yours.
VAG used 5 & 6 groove pulleys so make sure you have the right one. The shaft diameter may vary especially between manufacturers so pulleys may not swap where you want.
I will also note here that our alternators are all internal fan & internal voltage regulator. The voltage regulator is frequently the culprit of an inop alternator as the diode pack, windings, stator, et al, are more robust and don't wear as the brushes do in the regulator. However you must remove the alternator to pull the regulator off the back and it's really too much of a gamble for most people to do all that work just to test a new regulator. No one wants to do that twice just to test a theory. We don't mind doing the work, but you do it once and do it right the first time so you KNOW you either fixed it or you misdiagnosed the fault as an inop alternator (or you got a bad alternator out of the box which does happen).
I would invite any discussion about exciter wire voltage as I don't know enough about that aspect. It seems like a simple process whereby the alternator produces output in multiples of the field generated by the exciter wire input.
Anyone have any ideas, or anything to add? Know of a VAG V6 160 amp application where the mount has the same part # as ours? Post it up, someone will try it. (Maybe me since I need one)

[glennda5id]

You might be overthinking this a bit. But here is my input.

Looking at an Allroad. I only see that Valeo made a 120Amp alternator - 06b903018EX

There are also a couple of 140Amp alternators listed. Two by Valeo - 078903016AC, 078903018X and one by Bosch - 078903018AX.

The next step up is the water cooled 190A alternators.

Interestingly, valeo sells an two aftermarket alternators. One is 140A and one 150A. Both are listed as compatible with the 140A alternators above. But it is not listed as an alternative for the 120mp which makes me think it won't fit or it won't plug in.

http://www.rockauto.com/en/moreinfo....629700&jsn=362

and

http://www.rockauto.com/en/moreinfo....sn=363&jsn=363

[62willys]

You might be overthinking this a bit.

Haha... Ya think?! It's 100% my MO
I'll beat that horse after it starts to smell...

As far as the part #s go;
My allroad is an 01 2.7t with part #078903016AB. I believe this is the factory alternator since it has an 01 stamp on it. I'm not the original owner so I can't be sure but the date stamp makes me think it is factory fitted.

[62willys]

As far as swapping the 120 to 140 amp, I've read in this forum and others that's it's commonly done. Anyone with direct experience in this care to set the record straight? Do the plugs work?

[JTown77]

I would seek out your local auto electric shop, there is one in every city hiding down an alley in an industrial park. Often good people who rebuild altenators for less than you think with better internals than you get other places. They can even, if the case allows, increase amperage in the rebuild.

[62willys]

I would seek out your local auto electric shop, there is one in every city hiding down an alley in an industrial park. Often good people who rebuild altenators for less than you think with better internals than you get other places. They can even, if the case allows, increase amperage in the rebuild.

^this is actually my plan. In doing all this research I've found that rebuilds frequently are not of the same quality as oem even when rebuilt by the respective manufacturers.
I've tentatively settled on doing the tb service and finding a starter & alternator place to rebuild my alt while I'm wrenching on the rest of it. I might even consider pulling the starter and having them rebuild that too since it has as many miles on it as the alternator does. Car will be down anyway... Once and done, right?

Like I said, I still would like to compile our options for forum member in the future. No sense in someone else digging up my horse to beat...

[glennda5id]

The Valeo 439392 is a brand new alternator. I also do not trust remans. But I can't imagine a new unit made by an OE supplier is not going to give you more life than a local rebuild.

[62willys]

I believe you are accurate with that assessment. A NEW OEM alternator is probably the most reliable solution. That said, I will submit to you all that the closest equivalent to that per dollar is a local rebuild. Between those 2 (cost wise) lies several iterations of rebuilt solutions including;
OEM reman by Bosch or Valeo.
Reman by other "reputable" companies
Reman by other less than reputable companies

My take is this (with a caveat that a local rebuild is highly dependent upon the ability / quality of your local shop);

A Chinese or other "less than reputable " rebuild is a crap shoot. Good luck.
A "reputable" rebuild is lower risk than lesser rebuild and higher risk than an OEM rebuild.
An OEM rebuild is lower risk than all but new OEM (unless you have an excellent local shop.
A new OEM is the most expensive and rightly so since you get what you pay for when it comes to alternators. The only exception to this is if you have a reputable local rebuilder, you can get yours rebuilt to a high quality for less than a Chinese reman.
Reputable local rebuild = best bang for your buck especially with our cars getting so long in the tooth.
OEM new = most reliable, longest lasting (on average)...

[62willys]

Part numbers: (I'll update this if more are posted)
078903143N - 2.7t alternator mount bracket (01-05)
078 903 016 AB - 140 amp Bosch
078 903 016 AC - 140 amp Valeo

[AllroadFriendly]

I know this is a super old post but what was your outcome with this? I need a bigger alt and I’m not finding choices for upgraded alts. I’m gonna call Mechman on Monday and see if they can help. They don’t have anything for audi on the site but have some for vw so hopefully they can easily do something. Previously I had Singer alts build me a 250 amp for my ‘12 tdi sportwagen but they won’t even call me back 🙃 keep your fingers crossed!

[PaperToast]

I know this is a super old post but what was your outcome with this? I need a bigger alt and I’m not finding choices for upgraded alts. I’m gonna call Mechman on Monday and see if they can help. They don’t have anything for audi on the site but have some for vw so hopefully they can easily do something. Previously I had Singer alts build me a 250 amp for my ‘12 tdi sportwagen but they won’t even call me back 🙃 keep your fingers crossed!

not gonna happen
that person hasnt logged in for over 3 years

[RigsPGT]

I had a charging issue on my 03 Allroad and first I bought a used Bosch which judging by the cluster picture, the voltage read higher than mine. Swapped alternators and got similar readings like before so since I had my original out, I decided to buy a voltage regulator off of FCP. It was $29 for the part at the time (F00M144136)
Sanded down the contact area in the shaft where the brushes touch (used 400 grit) and installed the regulator.
Installed the alternator and the readings in the gauge have been improved but driving at night with lights/fogs and AC ON the needle drops to around 12.5V.
From the reading I've done, one of the major problems in our cars is the thin gauge cable from alternator to battery so even if your alternator might pass the test, charging might still be weak.