Alternator Bearings?

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Psucamper
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Alternator Bearings?

Post by Psucamper » Thu Jul 21, 2016 2:44 pm

I have a 55amp alternator that I removed from my 79 bus. Specifically it is the AL75x unit. Voltage output prior to removal was Ok but either one or both bearings are noisy.
Did the main B+ diodes test for forward current flow and they are Ok. No back current leakage. Cannot test the D+ set of diodes off-car. Electrically believe it to be a good/fair unit. My question relates to the end bearings. What are the part numbers and sizes for the commutator end and the driven end? Either the VW part numbers or mfgrs numbers. I can cross reference. Currently I have the following;
(2) SKF 6202 2z JEM 35x15x11mm (111-903-221A)??
(2) SKF 6201 2RS JEM 32x12x10mm (035-903-221B)??
(1) SKF 6201 Z/C3 32x12x10mm
The suffixes after the numbers appear to relate to the number and types of shielding on the sides of the bearing. What fits this alternator? Do any of the above fill the bill? What type of shielding is appropriate? Knowing the actual bearing dimensions can help in finding an appropriate bearing. I hate arcane questions like this! Thanks for any insight. Bob.

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SlowLane
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Re: Alternator Bearings?

Post by SlowLane » Thu Jul 21, 2016 4:34 pm

Psucamper wrote:I have a 55amp alternator that I removed from my 79 bus. Specifically it is the AL75x unit. Voltage output prior to removal was Ok but either one or both bearings are noisy.
Did the main B+ diodes test for forward current flow and they are Ok. No back current leakage. Cannot test the D+ set of diodes off-car. Electrically believe it to be a good/fair unit. My question relates to the end bearings. What are the part numbers and sizes for the commutator end and the driven end? Either the VW part numbers or mfgrs numbers. I can cross reference. Currently I have the following;
(2) SKF 6202 2z JEM 35x15x11mm (111-903-221A)??
(2) SKF 6201 2RS JEM 32x12x10mm (035-903-221B)??
(1) SKF 6201 Z/C3 32x12x10mm
The suffixes after the numbers appear to relate to the number and types of shielding on the sides of the bearing. What fits this alternator? Do any of the above fill the bill? What type of shielding is appropriate? Knowing the actual bearing dimensions can help in finding an appropriate bearing. I hate arcane questions like this! Thanks for any insight. Bob.
The 620x bearing numbers pretty much universally identify the size of the bearing across most manufacturers. The rest of the letters/numbers indicate various shields and seals.

I looked into this a little bit last year for my alternator. and one takeaway I had was to look for the 'C3' designation. This indicates a bearing intended for use in an electric motor. C3 bearings have extra clearance (ie. slop) in the bearing to account for thermal expansion. I took an intuitive leap to the conclusion that this would apply to an electric alternator just as well as to an electric motor.

Try VXB as a source for bearings of any sort you might desire. They carry Nachi bearings, which are very, very good.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
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