Alternator bearings

[tea boy]

I am rebuilding my alternator, do I use standard bearings or do I need C3 type extra clearance ones for high temperature?

Thanks.

[tea boy]

Well, if nothing else I’ve learnt that the 38 people who have looked at this don’t know the answer to my question.
I wonder if anyone does?

[impmad2000]

I too am curious for the answer.

[911hillclimber]

Ask Simply Bearings who supply many types for many applications?

[Gary71]

Yes. Extract what’s in there, measure them (or even check the number engraved on the side) then ask Simply Bearings.

[Bruce M]

If it’s not worn off (I’m guessing it is) the C3 would be marked.

[tea boy]

Thanks for the replies chaps.

I'll explain where I am with it.

Firstly, the alternator is for a 993, though I'm sure the information we need would be equally relevant to the 911.

The front bearing in it is a specific alternator bearing, so I can't go wrong with that. (It's a NSK B17-99DW8 by the way.)

The rear bearing is a 6201 2RS, which is just a standard sized bearing.

The one I removed has NTN 6201 CS20 printed on the outside and 6201LU on the rubber seals.



I have found that LU means that it is a contacting seal and that CS20 means 20 microns clearance but I have not been able to discover what the standard or C3 clearances would be.

Ideally I would just buy exactly the same NTN bearing but I have been unable to find any, hence my original question.

The old bearing has noticeable movement in it but that could just be because it is worn out.

I may just have to take it to a bearing specialist (when I can) and see what they say.

[911hillclimber]

Again, Simply Bearings would be a good first call as you have all the info they will need.

[tea boy]

Again, Simply Bearings would be a good first call as you have all the info they will need.

Cheers Graham, I’m awaiting their reply.

[tea boy]

Had a reply from simply bearings, they offered an alternative bearing which was totally the wrong type, so I’m awaiting their next suggestion, though I must say I don’t know how confident I feel about what they may offer me next time...

[911hillclimber]

Yes, that's dissapointing.
They sorted two bearing issues on my 1950 France crankshaft bearing issues which were quite high speed but lubrication by petrol/oil 2 stroke mix.
Fingers crossed for their next suggestion.

[hot66]

I just gave my alternator to my local guy who rebuilds them .. he had access to all the correct bearings. Do you have an alternator reconditioner near ?

[Ian Comerford]

I’ve used these people before and they were helpful, may be worth a call to ask them. https://www.burghfieldstarterandalternatorcentre.co.uk/

[inaglasshouse]

Not sure if you've seen this? 964 but must be close.
Well played to the original poster - it's an impressive technical write up.
http://forums.pelicanparts.com/porsche- ... build.html

[tea boy]

Not sure if you've seen this? 964 but must be close.
Well played to the original poster - it's an impressive technical write up.
http://forums.pelicanparts.com/porsche- ... build.html

Thanks, that’s a very helpful write up.
It’s basically the same except mine has a different front bearing.

I’m still waiting for simply bearings second suggestion, he said it might be a C3 bearing but needs to look into it.