Pelican Parts Forums - 964 alternator rebuild

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- - 964 alternator rebuild (http://forums.pelicanparts.com/porsche-964-993-technical-forum/686617-964-alternator-rebuild.html)

Alt. rebuilder replaced the two rear bearings, repacked the fan hub bearing. But I just inspected it because I thought it looked wet, barely pressed my thumbnail into the seal and it split. So a new one is in the mail for $110.

Also just picked up my fan and housing and I think it won't be necessary to sand the fan blade edges, as it spins freely.

Small questions if I may. I have been told that on idle or on revving (1500->3000) a voltage greater or equal to 13.8 to 14.4 could and should be achievable ( no higher ) . My battery died most recently .... The voltage read at the battery at idle is 13.55V ; Even if I am revving above 2000 ---> 3500 RPMs that voltage never changes - it actually sometimes drops to 13.45V at times while revving. Is this abnormal and should it warrant a closer look at the alternator , perhaps a rebuild ? Any and all insights would be so very welcome. Thank you .

Am about to do this on the 3.6 in the car. Now that summer is here when I turn on the A/C am seeing voltages in the 13.4-13.4 range while driving and thats just too low for me.

I have had the engine for 10-12k miles and I contacted the previous owner and he said that he had not done anything to the alternator, so guessing that its stock and that means that its got just over 100k miles on it now.

Great writeup! Did any of you guys see an increase in voltage with the overhauled unit? This one I am doing is in a transplanted 1985 911 so very little electronics like you guys have in the later model cars.

At idle, mine reads about 13.6- 13.8 VDC at the battery terminals with all electrical loads ON. I use a Fluke digital meter.

Quote:

Originally Posted by bazar01 (Post 8661027)

At idle, mine reads about 13.6- 13.8 VDC at the battery terminals with all electrical loads ON. I use a Fluke digital meter.

Thanks and what do you see while you are running? Am guessing in the low 14's?

Was driving home the other day at night so had lights and the A/C on and at times the voltage dipped down to 13.0.

IMHO for a 115 amp alternator thats far too low and it should hold the load with no issues. Time to overhaul this one...

Quote:

Originally Posted by Joeaksa (Post 8661241)

I measure 14.0 to 14.2 at the battery at idle with whatever loads are on while running.

If you look at the alternator label, it reads 115A 14V, so you should not be anywhere below 14V with only those loads on. Note also that spec is not at idle RPM, but usually at a few thousand "alternator" RPM which runs higher than engine RPM due to pulley ratios.

Quote:

Originally Posted by Traveller (Post 8663064)

Except for a battery with a dead, shorted cell.

Screws are immovable! (Bathed in WD40)

Quote:

Originally Posted by JWPATE (Post 6835224)

http://forums.pelicanparts.com/uploa...1341251092.jpg

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.

http://forums.pelicanparts.com/uploa...1341251287.jpg

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.

http://forums.pelicanparts.com/uploa...1341251725.jpg

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.

http://forums.pelicanparts.com/uploa...1341251928.jpg

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.

http://forums.pelicanparts.com/uploa...1341252172.jpg

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.

Hi,
I'm stuck. I can't get these #!%#$@ screws out.
Any/all advice appreciated.
Thanks,
John

Quote:

Originally Posted by johnhedge (Post 8982737)

Hi,
I'm stuck. I can't get these #!%#$@ screws out.
Any/all advice appreciated.
Thanks,
John

Impact driver with a properly fitting bit, or as a last resort, a set of Vise-Grip pliers.

Quote:

Originally Posted by Traveller (Post 8982881)

Impact driver with a properly fitting bit, or as a last resort, a set of Vise-Grip pliers.

I bought a driver a few years ago but I hadn't realised it was an impact driver. I tried it and they came out sweet as a nut!

Great advice.

Again thanks.

Quote:

Originally Posted by JWPATE (Post 6835224)

http://forums.pelicanparts.com/uploa...1341251287.jpg

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.

Every notice something about that?

The problem is, for those longer hex head bolts to come out, the pan head screws would have to loosen....BUT...there is nothing locking the pan head screws in place.

Those tabs would need another section of metal on the other side that could be folded over the flat of a hex head bolt that should be used instead of a pan head screw. And if the nuts holding the long hex head screws are tight, those screws could never come out. And if you are going to say the nuts on the hex head bolts might loosen, then you might as well say the pan head screws could loosen as well.

OK, so the pan head screws may never have loosened (mine are still tight), but for the idea that Bosch used in this instance, it would never fly in the aviation world.

Another possibility is that they intended to use a hex head bolt to hold the alternator halves together and you would then bend the tab over to lock the bolt in place.