964 alternator rebuild

[JWPATE]

OK, the above is only a typical alternator from Bosch, but the units in our 964 cars are not much different. So it is a good illustration of what will be involved.

In my case, the original unit is still performing its duties well. What I have, is an occasional and faint whine from the engine bay. It could be one of several several bearings starting to fail. Could be one of the two in the alternator, could be the duel design cooling fan bearing, or could be the AC compressor rear bearing. All of these have one by one been changed over the last few years, except for the alternator. So I am going there next.

Yes, it also could be just a belt that from time to time decides to whine a little.

I prefer to do the rebuild myself, if I am able to, because that way I will retain the original alternator, which is doing just fine. And, this way I will know just what replacement bearings are used.



So, I hope those happening upon this thread will point out my mistakes, or just suggest another approach when a better way to skin this cat is out there.
I wanted to just skip over the removal and replacement steps, but honestly, the workshop manual is not at its finest in this procedure, so better go through the steps.

For a start, the manual states that a protective cap needs to be removed before taking off this 24 mm fan nut. Has anyone ever seen a protective cap on this nut? I haven't.




And, if there is air conditioning, we actually must begin here with the compressor. Those bolts are 13 mm head and to remove the belt, it is necessary to remove at least the outboard two and the inboard rear, while loosening the remain bolt and the shorter bolt at the hanger bracket. Then the compressor can be tilted, and the belt removed.




Before starting, I did think to check the belt tensions with that little Porsche tool. They all three were in spec. (15-23 on the metric scale). So here I am careful to keep the shims in place, exactly as they were on the engine.




This washer comes off next. Be sure to note that it is cone shaped on one side, and the cone goes forward.

A 5 mm Allen is needed here to remove the three screws. Then take out the fan pulley screws. Count the shims here too and store them with care. You will find that the shims and pulley halves have locator holes, which must also line up with a pin, such that they only can go on one way.



Next we must get this section of air duct out of our way. Don't be tempted to think it can be removed after taking out that screw on top. There are two others, which are all but unaccessible. It is far better to take out the entire fan and its ducting, just is is done every time the car comes in for scheduled service.




That completed, we can now take a 10 mm socket and remove the screws which hold the upper cover in place.




The little cover comes out easily, after the three screws are removed.




And with the cover off now, it is possible to peer in the opening at the top of the engine, where the ground wires are attached.

Going to break here for lunch, and continue the effort later.

[JWPATE]

Now, with wires coming into view, it is time to disconnect the battery ground before going further.

Use a 4 mm Allen and remove the two screws holding the plastic cover to the fan housing. This cover protects the three upper ignition wires for the right side. Remove those three wire ends from the distributor, and position the wires and cover off to one side.



Next use a 5 mm Allen and remove the attaching bolt from the retaining strap. Take the bolt all the way out and open the strap ends away from the housing.

All that is now attached to the housing unit are the wires for the alternator, and they enter at the other end. They will not be easy to get at, but certainly they are within our capability. Just go slowly and carefully.




At this point, I decided it would be best to fit up a protective cover and move the air conditioning compressor right out of the way.

At the front end of the alternator, a cooling fan is attached and covered by a protective shroud, as Porsche calls it. We can now use a 10 mm socket or wrench and remove the four nuts securing that cover in place. The cover or shroud can then be worked off.



And, with the shroud removed it is possible to examine the alternator cooling fan. It could be removed at this point, but I prefer to save that job for the bench.

Look under the fan, and observe the wires, which must next be removed. First the large red wire to the battery is released. Then we will find a small gauge blue wire, which comes off next. Both of these are on the passenger side.

A brown, ground wire is on the driver side, and it is attached using a Phillips screw. You will find that the cooling fan prevents a straight on attack at that screw. Still it came out without a problem in this case. If it couldn't have been started out, then I would next have looked at taking off the fan.




So, with those three wires disconnected, the entire fan housing can now be lifted out and taken to the comfort of a bench.

I am not proud of this method for removing the engine cooling fan, and was worried about damage to the fan. It went OK though and was not a tough pull at all. I believe it might make a better job of it however, to use long M6 bolts in those threaded holes, and a three bolt puller. I had the puller, but not bolts that were long enough, and didn't wish to wait while ordering them.

I would like to know how other have done it though.



With the fan wheel pulled off, it is now a relative easy matter to take off the housing for that dual action bearing. This was also a fairly easy pull, using a somewhat more stout puller.





So all's well that ends well. It is starting to really warm up on this Nevada afternoon, so I will break off the effort for today and return to it in the cool of early morn.

[creaturecat]

nicely done (so far).
thanks

[JWPATE]

OK, and here is a look at the alternator cooling fan from the comfort of the bench. I am ready to take it off, but first it would seem the right time to remove the alternator from the fan housing.



Do not be tempted to remove these screws at this point. They have a joint function of holding the alternator case halves together, and also, by those little metal tabs, they prevent the larger hex head bolts from falling out of their bores. We removed the nuts off those hex bolts earlier, in order to take off the alternator fan shroud and get at the wires for disconnecting.

At this stage (with that shroud already off) there is nothing preventing the alternator from slipping out of the engine fan housing, except that it is snug in there.




First though, take time to note the position of those electric connecting points relative to the top dead center mark on the engine fan housing. I have the pencil pointing toward the mark here.



Now support the fan housing on wood blocks or whatever is handy, put something soft under to take the impact from the alternator shaft, then use a soft drift and gentle taps to persuade the alternator out of there.




And, finally we are able to see the unit out on its own. This is what they look like. Slightly different from that image at the start of this thread, but the image is the closest thing I could find. It also has been most helpful.

The BOSCH part number on that plate is 0 120 468 029.

I will take a break here before moving on to the main event.

[JWPATE]

First step will be to take off that cooling fan nut. It requires a 17 mm socket or wrench and some method for holding the shaft from turning. The only thing I know of which will get that job done, is the special tool which came with each car for changing fan belts.

The nut was put on with red loctite, and that is why I preferred to attack it here in comfort.



That fan is a strong little unit, but I decided none-the-less that it would be best to spread out the pulling load against it. I used a gear puller with the flat side in contact with the fan.




After the fan is off, there will still remain this spacer collar. I just couldn't be sure from the starting image, whether or this collar would foul when separating the case halves. So I set out to take it off.

Notice in the foreground of this image, that electrical device with the black plastic head. This is the voltage regulator and it serves also as the carrier for the electric brushes.



So, I locked that collar in the vice and turned the shaft inside it using the Porsche fan belt tool again. A few minutes with a good amount of the penetrating oil took the thing off.

Later on I learned that this step was not needed. It would have gone just as well to leave that collar on and pull it off later, along with the front bearing.



Ok, and now on to the necessary step of removing the electric brushes. The way to do it is by taking out the two Phillips head machine screws, and removing the voltage regulator, complete with the brushes.

Take a look at those brushes brother. They are near the end of their life cycle, without doubt. The car has done about 70 thousand miles now, so I have made a note that the alternator brushes should be changed every 60K.

It is possible to change only the brushes. However, I am informed that after brushes and bearings, the most frequent causes of alternator trouble is with the voltage regulator. So I shall change the complete unit. For a case where only the brushes are to be replaced, we want to order Bosch brushes for the 28 mm slip rings. New brushes are 4.9 mm x 7.9 mm x 19 mm.

Part number - Bosch 1 197 311027



Now is the time to remove the four machine screws I spoke of earlier, which fasten the case halves together.

Don't be mislead by the seeming ease seen in this photo. To start them out, I had to support the alternator on wood blocks and use an impact Phillips screwdriver. Thankfully they all came out without damage.





This is what you will have after the halves are separated. No hammer blows or pry bars were needed. They come open easily, until after an inch or so you reach the limits of the front bearing cage. Then just continue to bump the halves apart until you have pulled the front outer-bearing-race free of its cage.

Time for another coffee break.

[Sboxin]

Excellent write up and photos!
Thank you for doing this for the rest of us.
Now, I can do this while our engine is out and apart
(for a 964 rebuild/upgrade that will go into the UPS race car).

Question: how available are the parts?

Regards

[bazar01]

Originally Posted by Sboxin

Excellent write up and photos!
Thank you for doing this for the rest of us.
Now, I can do this while our engine is out and apart
(for a 964 rebuild/upgrade that will go into the UPS race car).

Question: how available are the parts?

Regards

Parts are available from Pelican.

You can also get the kit from here.

Alternator Parts - Starter Parts - Alternator & Starter Repair kits

Rectifier from here:

Alternator Parts - Starter Parts - Alternator & Starter Repair kits

[Sboxin]

bazar01 -- thanks for the parts link and info

Regards,

[JWPATE]

Originally Posted by Sboxin

Excellent write up and photos!
Thank you for doing this for the rest of us.
Now, I can do this while our engine is out and apart
(for a 964 rebuild/upgrade that will go into the UPS race car).

Question: how available are the parts?

Regards

Sboxin,

The parts are available as kits, from a number of sources. In this case however, I would recommend ordering only the OEM parts, and separately. For very much the same reason I am not willing to trade my original alternator for a "Remanufactured" unit. There is too much corner cutting in that business - aftermarket replacements include bearings from China.

The genuine voltage regulators, complete with brushes can be ordered directly from our host. Pelican also has the engine fan hub, complete with the dual action bearing. This latter item is a little steep, at over $200. But if it has never been replaced, then now is likely to be a good time.

Alternator bearings are another matter. Any bearing shop can match them with new units in the correct size. But, beware! Even some of the big bearing firms have shifted some operations to China.

Bear with me through the next phase in this teardown. One primary reason I decided to post this information for other members, is the simple fact that I could not find accurate bearing sizes for this particular alternator. I certainly would have preferred to have the new parts on hand before starting.

We shall soon have the information!

[JWPATE]

If we look down into the rear half of the case, it is easy to see the plastic housing, from which we just extracted the rear bearing outer race. I expect this plastic part is available, but this one looks just fine, and so I shall move on.




The slip rings look just fine also. I probably will smooth them with 600 or finer wet-or-dry paper, as I am waiting for parts to arrive. In the event that the slip rings were damaged, from waiting too long in replacing brushes, then new slip rings are available. If they turn out to be needed, we want to order the Bosch rings in 17mm ID and 28mm OD.

The rear bearing is easily accessible now, and I just pulled it off the shaft with the same two jaw puller seen earlier.




At the front case half, we are looking here at the housing for the front bearing outer race, and can imagine what these four Phillips are fastening. They pass through the case, and screw into a sheet metal, formed retainer. This plate can be clearly seen by looking at the starting image of this thread.

Remove the four screws, and the bearing is now free to come out of its recess.



No great amount of force will be required here. Just hang the case half in one hand, and gently tap that front bearing from its home.



Now, to remove the bearing from the shaft, you will find that there is little room to get a puller in there (I am already half way off with it in the photo). I found it was easier to put a gear puller in place, and take the sheet metal plate, bearing, and spacer all off together.

Make note that the spacing collar has a raised lip on one side. That side with the lip faces the bearing. The little lip contacts the inner race and thus provides a space to prevent damage to the rubber side seal.






Ok, that completes the strip-down phase of this operation.

These are the three items which just came off the rotor shaft. This front bearing is far larger than the rear. It takes all the radial load from the drive belt.



These are the three parts we will replace with new units.

The voltage regulator is BOSCH part number 1 197 311027

The smaller, rear bearing is ID 12mm OD 32mm width 10mm common size number 6201-2RS

The larger, front bearing is ID 17mm OD 47MM width 14mm common size number 6303-2RS

(the -2RS on both bearings means both sides have rubber grease seals)

With that information finally nailed down, I started to seek out the parts. The Voltage regulator is no problem, and for the bearings, I decided on ordering from:

SMITH COMPANY
530 11TH STREET
GREELEY, CO 80631
Smith Co Electric - Starters & Alternators, New & Remanufactured
970 353 3121

If you decide to try Smith, I suggest that you ask for Dave. He was helpful, and certainly knows what he is talking about.

Wherever you decide upon, do try and get the bearings in either OEM or one of the other respected brands, such as F.A.G., SKF, Timken, KOYO, NACH, OR NTN.

In this case, the originals were NSK Bearings. Dave is sending the OEM brand for the large, front bearing, and NTN for the smaller rear.

On hold now, until the parts arrive.

[JWPATE]

Because these are exactly the kinds of details which we first-timers can get wrong on the rebuild, I have decided to add another photo to better illustrate the front bearing parts in a previous image. I would have just changed that first photo with an edit, but couldn't see a way to do it.



The same three items seen in the previous image, but here orientated as they will be in the built up alternator. And in this photo the lip on that spacer collar is easily seen.

[JWPATE]

OK, so I was cleaning up the slip rings and examining other things, while waiting for parts.

One thing I wanted to do was examine the fit of those bearing outer races, without the rotor shaft in the way. The large front bearing can easily be pushed into and out of its bore with finger pressure. The retainer plate will further insure that the outer race doesn't spin in the case.

The smaller rear bearing uses that plastic cup I pointed out in an earlier photo. It too can be pushed in and out, but takes a good deal more pressure. In the process of testing, I heard the sound of the little plastic cup cracking. Arg!

From long experience I know plastic parts are past their life expectancy after 10 or 12 years. It looked ok. But now it isn't.



In order to take it out, we must go another step in the disassembly. First pull off the positive wire of that little capacitor from the spade seen here. No need to mark anything with paint dots, because on re-assembly we need only align that spade in its hole. There is none other like it.

Then take the nuts off the two terminals at the pencil's end with a 13mm and 8mm socket. The insulator block then can be removed from the terminals.




Flip the thing over,locate the five Phillips head machine screws, which fasten the rectifier plate to the rear case half, and take them out. The stator coils do nor permit a straight on angle at those screws. But they all came out with firm pressure.




The rear alternator case half can them be removed, which will allow us to get at that plastic cup.



This should probably be expected, considering the age of a 964 alternator. I do expect that this part is available, and will start looking tomorrow.

As it is, I don't even know what the thing is called. A rear bearing retainer cup???

We shall see.

[JWPATE]

Ok, the item is called a tolerance ring by Bosch. More commonly it is referred to as a bearing retainer.

They are easily available, and the best site I have located for small items such as the bearing retainer is:

Wagner Alternators and Supplies, Inc. Use the link below for a great listing of parts.

Wagner Alternator Products Catalogs

They have several shipping points and are happy to send out parts retail. This has been a great find, in our search for alternator parts. The bearing retainer is found on their catalog of small parts under the number W110-21.

[JWPATE]

The new "tolerance ring" arrived today, and is shown here for comparison with the broken original. The new one is also in plastic, clear rather than white, and made in Taiwan. Should you need to order one from Wagner, they have assigned it the order number seen above, W110-21.

[JWPATE]

An earlier photo of these slip rings show the grooves, which the brushes cut into the brass over 70+ thousand miles.

I don't have a lathe here, so took the rotor over to a specialist today. He was kind enough to allow me to stand nearby and watch, as the slip rings were skimmed clean on the lathe.

Just about .5 MM came off each ring, all the way around. They started life as 28 mm rings and now measure 27 mm. After another twenty years, when they again need attention, it will probably be best to replace them with new rings. That will be a concern for someone other than this old boy.




The two OEM bearings have arrived, and again the correct sizes are 6303-2RS for the front bearing and 6201-2RS for the rear.

As were the originals, these bearings are both NSK brand. The originals were made in a plant in England, and these replacements were made in Poland.




Here, the new regulator is compared with the original. Note the brush length of the new, compared to 70K miles of wear.

[JWPATE]

We start the buildup by replacing that broken plastic bearing retainer. Like the original, the replacement unit has an opening in the skirt (lower right in this image-not easily seen though) to provide space for the brushes. To make sure the opening is correctly positioned, a tab is provided in the plastic, which must fit onto the notch opening in the alternator case, as shown.




Next, line up the five machine screws, which fasten the rectifier plate to the rear alternator case half. Be careful to position the insulator sleeves correctly at the two wiring posts.



Flip the case over, and replace the insulator block. Plug the capacitor wire back on its spade connector (I believe this capacitor is fitted to eliminate any possible radio static).






We start here, with the smaller rear bearing. Its spacer sleeve is an easy to use tool in pressing the inner race onto the shaft. Just locate something handy, like this socket, to extend the thing well past the end of the shaft. Press it fully home against the shoulder where the shaft increases in diameter.



For the front bearing, be sure to place on the retaining plate first (correct orientation as seen in an earlier photo).

For the press operation it is again best to use the spacing collar as part of the pressing force. I jury rigged up a VW gear tool with a collar to extend the cylinders well past the shaft end.

These press operations are all easy push-ons, requiring very little force.




And, almost quicker that it takes to explain it, we wind up with the rotor built up and ready to go back into the case.

We shall start with the front case half, and with everything now clean, the front bearing just slips into the case recess with no force needed. It will be held from spinning by the retainer plate.




Use a punch, or what-have-you, to line up the retainer plate, and replace the four machine screws.




Now we bring the two case halves together and begin to force that little rear bearing into the new plastic retainer. I could get it about half way with hand pressure alone. Younger members can likely push it all the way. For me, I took it over to the press, and gently moved it home.




Replace the long bolts for the rear cover, and then take up the four case-to-case machine screws. Good and firm with them, but I didn't use any thread lock.

And with the alternator rebuild completed, I shall take a coffee break.

[JWPATE]

There are three bearings on that alternator shaft. Small wonder that the larger front bearing doesn't last forever. In addition to the alternator drive belt, it also must take the radial load for this, the engine fan bearing and its drive belt.

Anyway, I wasn't sure just which bearing was starting to whine, so thought it best to start fresh with all three new.

This is an interesting image. Notice that the original engine fan bearing is pressed into the hub, and retained there with a standard inside snap ring. The ring could be removed, the bearing pressed out, and a new bearing fitted.

Now look at the new fan hub. That bearing also was pressed in. But! It is retained in there with a non-removeable style ring. This hub is a one-shot combination. I notice it was Made in Slovakia. Oh yes, this hub is the Genuine Porsche part for 2012 - and they don't make um like they used to.

I am going ahead with the Slovakia hub and bearing. But I am also going to press out the old bearing & see whether a new quality bearing of that size can be located.




Carefully line up the three holes in the hub with those in the fan, and press the hub fully home from the back side.



Place the spacing collar on the alternator shaft, and press the fan on using a sleeve to place the force only on the inner race of that hub bearing.

For the alternator fan, I am going to wait and put it on after the wires are connected. It only takes 10 ft.lb. of torque when going on, and that will be easy enough, even for myself. The wires will be easier to deal with with the fan off, especially the ground, which uses a Phillips head machine screw.



With everything clean, you will find that the alternator slips easily into the fan housing. So easily, that it will be helpful to fit washers or some other spacer as shown here, to keep things snug while hooking up the wires.

With the three wires connected up again, first put the rear fan on the shaft, use loctite 270 on the nut and ten pounds of torque to secure it.

Now take off the temporary spacer washers, and replace the rear cover. Snug up its four all-metal lock nuts, and continue to replace all the routine items in the reverse order we used to remove them.



I cannot say for certain which bearing was beginning to whine, but the loading would suggest it probably was the alternator front bearing. Anyway, the test ride confirms that all is quiet again now.

And this will wrap up the Pelican thread on 964 alternator rebuild. I have already pointed out the new bearings and other parts needed, as well as where they may be obtained, so will not repeat that information here.

Some of the torque settings might be helpful though:

Strap bolt to secure engine fan housing 6 ft lbs
Alternator fan nut (with loctite 270) 10 ft lbs
Alternator pulley nut 37 ft lbs
m6 Allen screws at engine fan pulley 7.5 ft lbs
A/C compressor hold down bolts 21 ft lbs


Using the Porsche belt tension tool and with used, cold belts

Alternator belt tension 15-23 units
Engine fan belt tension 15-23 units
A/C compressor belt tension 30-35 units

[mb911]

Curious What was your cost to do this in parts?

[JWPATE]

Originally Posted by mb911

Curious What was your cost to do this in parts?

Good question Ben, and thanks for reminding me. I should have included that information, for certain. Not including shipping costs, which will vary with distance, the cost breakdown for the alternator rebuild is:

Bosch voltage regulator w/brushes 63.04
6303-2RS OEM bearing 33.28
6201-2RS OEM bearing 29.95
Plastic rear bearing retainer 6.95

Parts 133.22
Turn rotor slip rings in lathe Service 25.00

Total parts/service 158.22

[mb911]

You did such a nice job on write up and rebuild . My question is aren't rebuilt alternators from bosch about the same price? I thought so but I would have to look at my records. Though the nice thing is you know exactly what you have with doing it yourself