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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: conybeare on May 05, 2012, 11:13:51 PM

Title: Should alternator spin freely?
Post by: conybeare on May 05, 2012, 11:13:51 PM

I just bought a used 50A alternator off of FleaBay and plan to get it tested at an auto parts store soon. I noticed that it only turns semi-freely about 3/4 of a turn in either direction before it locks - is that normal? Not sure if it should spin freely around and around...

Title: Re: Should alternator spin freely?
Post by: frankenduck on May 05, 2012, 11:15:49 PM

No. Not normal.  It should spin "fairly" freely.

Title: Re: Should alternator spin freely?
Post by: conybeare on May 05, 2012, 11:29:12 PM

Damn - thanks for the info. Time to contact the seller...

Title: Re: Should alternator spin freely?
Post by: conybeare on May 05, 2012, 11:37:02 PM

Speaking of alternators... what is the lifespan of one of the 50A ones? Do they tend to die out after 100k or so?

Title: Re: Should alternator spin freely?
Post by: wmax351 on May 06, 2012, 12:15:17 AM

I rebuilt mine (from frankenduck). Had a bit of notchiness in the bearings. The fan also brushed the housing at one spot. A minute with a pair of pliers fixed that. I posted up the rebuild info in the lieberry (http://www.motobrick.com/index.php/topic,788.0.html).

Title: Re: Should alternator spin freely?
Post by: conybeare on May 06, 2012, 01:35:14 PM

Thanks for the info, wmax. I took the alternator apart this morning and although I couldn't quite tell what was catching, I guessed that it was the inner edges of the fan catching on the inner part of the housing. I bent some of the fins that were especially close to the center, reassembled, and all seems to be well!

The guy I bought it from said he had tested it - and I believe him - I just don't know how it was working if the fins were catching like that... Maybe once it was powered the fins just scraped past. Anyway, thanks both of you for the help!