rjhuhn

10+ year old non OEM 1 wire alternator began protesting at start up and continues for 10 minutes of driving, or so. Running a serpentine belt (for many years) drive. Recently replaced belt. tensioned to 1/2 inch deflection. Would like input before investing in a new alternator.

dplotkin

If you are certain its the alternator replace it. Bearing failure is not typical but it happens, usually from overtight belts.

Dan

MikeM

If it charges okay, why not just put a new bearing in the alternator?

I disagree that bearing failure is not a common occurrence.

Your belt tension seems awful tight to me.

Frankie the Fink

Bearing failure seemed to occur more years ago for some reason but yeah that's what it is....a shop can press in a new one or I recall having done it once or twice myself years ago...

dplotkin

Mike: I can only speak for my own experience and that of others I know which is that later model GM alternators do not experience bearing failures as often as that of 10DN units and generators (whether Delco or Autolite). They do fail, but not often and when it happens its almost always too tight a belt. I believe the age of the serpentine belt has something to do with that.

Far more likely to fail on these is the internal regulator and eventually the brushes that ride on the slip rings. Even diodes almost never fail as they once did.

My advice to the OP would have been to replace the bearing if he had the original or correct or almost correct 10DN. But a parts store 1 wire? I'd just as soon swap it than fool around with a AutoZone alternator or one borrowed from a farm tractor.

Just my view...your results and thinking may vary.

Dan

MikeM

No, I agree 100% with your revised statement.

I've had cars with the 10DN alternator that were still charging but the bearing was really noisy. They were noisy when I got them with the exception of a couple that had 150K+ miles on them. I don't think I've ever changed out a 10DN because it wouldn't charge.

I have always run V belts just tight enough to keep them from slipping. I never get close to the factory spec tension but I understand why their spec is what it is.

Frankie the Fink

I adjust fan belts for about 1/2" deflection with a firm thumb along the longest length...that's always worked for me. Serpentine belts like the OP has, I don't know, I thought they had an idler tensioner that maintains the adjustment...

Easy Rhino

I thought so, too.

Other than the dress-up, what is the purpose of the serpentine belt systems?

rongold

More surface area---More grip, But I just went out to my new car with a serpentine belt and automatic tensioner, and there is no more than 1/8-1/4" of movement at the longest span of the belt. I think your belt is slipping and making the screeching noise !!!

dplotkin

They were introduced primarily for uniform tightness, eliminating the need to tighten 3 or more belts, and to manufacture and stock more than one belt per car...and...wait for it...to eliminate the phenomenon of over-tightening and blowing bearings! That's why I think the incidence of bad alternator bearings is reduced.

Why they are used on classics and hot rods escapes me but lots of things do...

Dan

rjhuhn

Thanks for all the input. Installed a new Powermaster 100amp single wire alt. It was curious that the install instructions had BIG warnings about how to tension the belt to avoid damage. It said to continue to tighten until, when turning the alternator with a ratchet, the engine turns over rather than the belt slipping. That was considerably tighter than I would have done using deflection.