What could cause my Geo to blow three alternators in 13 months?

Dear Car Talk

Dear Car Talk | Feb 01, 2000

Dear Tom and Ray:

I own a 1993 Geo Prizm LSi with air conditioning. I have put in three alternators
in the past 13 months. Is there anything you know of that would cause them to
keep blowing? -- Steve

RAY: There are two things I can think of. One is that you're putting in lousy,
rebuilt alternators. The quality of rebuilds varies tremendously -- from real-
cheap junk to not-quite-so-cheap junk. So that could be the problem.

TOM: Just as likely, though, your alternator belt is too tight. An over-tightened
belt will fry an alternator faster than just about anything. The rear bearing of
the alternator is often built into the diode bridge. And when the bearing fails,
the alternator stops producing electricity.

RAY: But there's no good electrical reason why the alternators should be burning
out so fast. You're not playing the radio too loud ... or lighting up your neon
fuzzy dice too often. So start by asking someone to check the belt, Steve.

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