Failing alternator bearings?

[s_wilwerding]

What do failing alternator bearings sound like? Sometimes, both at idle and under power, there's a noise coming from the alternator area. It's difficult to describe - it's not a knocking sound, more like the sound a wobbly moving part would make. Could this be the alternator? It still seems to be charging fine and it doesn't always make the noise, but I'd just as soon get it fixed before it does go out.

Thanks.

[Sean Hamilton]

Hmmm, sounds familiar. Try here:-
Fan Wabble - 1980 SC

[s_wilwerding]

Originally posted by Sean Hamilton
Hmmm, sounds familiar. Try here:-
Fan Wabble - 1980 SC

Thanks - mine is almost exactly the same problem, though my fan is not contacting the shroud. I'll have to pull it out this weekend and take a look.

[Sean Hamilton]

Steve, I was thinking yours maybe an internal noise? Per Jim's post:-

Originally posted by Jim Sims
I confirm what Moses says about internal part damage. The "wobble" of the rotor can also chew up the brushes. I lost the brushes in one of mine (alternator light came on dash) about the same time the fan wobble showed up. If the wobble gets bad enough it will damage other parts to the extent that the rotor can't be repaired. Have the internal parts checked too. Make sure the bearings are pressed on by applying force only to the inner races. Preheating the bearing with a special bearing hot plate or hot air gun helps reduce the force required to install them. Have the internal parts checked too. Jim

Good luck. Keep us posted.

[john walker's workshop]

remove the belt and run the engine. see if the noise stops. but before you do that, do a belt noise test. spray a quick blast of WD on the lower pulley groove with the engine running and see if the noise goes away for a minute or so.

[Sean Hamilton]

Originally posted by john walker's workshop
......do a belt noise test.........

Yes, and that brings up a new issue John - how do you remove the "belt noise" permanently?

[john walker's workshop]

just replace the belt when it gets noisy. the sides get polished from going around the pulleys, so they get kind of creaky sounding after a while. some brands are noisier than others. i use continentals, but they all have the potential to be noisy with time. a bit looser on the adjustment will help, but not too loose so it slips and squeels.

[Superman]

Or you can "recondition" your belt. Hold some sandpaper or the edge of a screwdriver against the contact surface of the belt, carefully, with the engine running. This will stop noise. Heck, any liquid will stop the noise temporarily.

You can place a stick against the air shroud behind the fan while the engine is running and listen to the alternator bearings. when they get tired, they rattle.

[s_wilwerding]

OK, assuming the bearings are going bad (which I don't know yet), where is a good place to get the alternator rebuilt? I suppose it's asking too much if anyone knows of a good place around Omaha? Alternatively, where could I buy a rebuilt alternator? What would fixing/buying an alternator cost?

I appreciate everyone's help.

P.S. I'm quite certain it's not the belt, but I appreciate you guys bringing up the idea.

[Sean Hamilton]

Steve, I had mine rebuilt by a local Auto electrician. There's nothing all that unique or special about the assembly or components.
More important is that the Auto electrician source quality bearings and does an expert job in the rewinding, bushes and assembly etc. Mine came back as brand new and only cost $300.00 Aus.
"I" just had to make sure that I reconnected the wires in the corrected sequence and to the correct terminals.
All done in a week and I was very satisfied when I finally started her up - no noises and perfect voltage.

PS. I did what Super suggested - a plastic hose as a stethoscope. It works.