usassh

Hello,

I have a 1986 C20 Chev Suburban with 454. In December 2009 the alternator gave up the ghost and I replaced it with a Checker Auto Parts Ultima Alternator 01-1015 (94 amps).

This alternator ran great until May 2010 when it began to squeel VERY loadly. I changed nothing during the time frame that it worked fine (i.e. no belt change, tension was the same deflection, and the tightening bolt on the positioning rack/bracket was in the same location on in the swivel position).

So, I took the Alternator back to Checker and they gave me a new one. I got another "identical" reman Ultima 01-1015. But . . . this one is worse than the first one. I have tried the original tightening position on the swivel rack (wicked squeel), so I tried more tension, (worse wicked squeel), so I tried much lesser tension. In the case of the much lesser tension the belt-to-pulley tension is so loose that I can spin the pulley as if there were no belt impeding movement. But at least the squeel is minimized (i.e. very minor squeel in park, but the banshee squeels horribly as my speed increases.

This reminds me of Goldie Locks and the Three Bears. Too tight squeels. Too lose squeels. The original marked bolt tightening poistion on the swivel rack squeels. And I have tried at least 20 other slow progressive intermediate positions leaning to the tighter side and also to the looser side.

I am losing my mind.

Now I do not drive it except to test, so I have not been out and about wrecking the belt nor trying to overly stress the bearings. i.e. now more than 4 minutes driving per test.

So, Ultima Alternator 01-1015 worked from Dec 2009 thru to May 2010.

So, what have I considered:

1) Pulley threads (I have six and they match the belt)

2) Mounting rack/bracket. There are three bolts.

2A) The swivel bracket the the main one that changes are adjusts tension.

usassh

2B) The swivel bracket also attaches to the engine housing (was missing a bolt but the position does not change). So, I did add a bolt. This really cannot move so my bolt is more because the nuts was there.

2C) The swivel bracket also has a lower brace. The brace was completely missing the long 4"-to-5" bolt. This would server as a pivot point for the swivel bolt location. I admit that this could be the problem. So, I let it go to a natural position and used washers to ensure that position was maintained as I added the missing bolt to not allow the position to change as the bolt was tightened.

Keep in mind these two "missing bolts" were missing for years and were missing on the first dead alternator (Dec 2009) and worked "fine" on the new Alternator from (Dec 2009 to May 2010).

I believe the squeel comes from the Alternator shaft bending upon tension causing bearing to scream (tight, loose, many middle positions). But what explains the same squeel sound) when the tension is such that I can spin the pulley as if the belt were not even there.

I am thinking about trying another brand (to isolate the real source). My 1989 suburban (yes, the CFO let me have more than 1) has an Autolite Pro-Tech that behaves it self and runs like a champ.

I am about to remove the lower "bolt" that is the swivel point.

Long Live Suburbans . . .

-- Steve

73shark

I assume you're sure that it's not the belt squealing. Is it a serpentine belt? If so, doesn't it have a spring loaded idler that maintains tension? The idler bearings wear out and will make noise 'til they freeze up.

If it's a V-belt and it might be squealing, then if you spray a mist of water on it, the squeal will stop if it's the belt.

gotstylez

easy way to eliminate the alt. is to spray some wd-40 into it..it shouldn't hurt it..

usassh

OK. Here was the problem. While working in the dark tonight I decided to flip the belt around (just in case one outside was slightly longer than the other). While doing so and after tighening down allowing for about 3/4 inch play in the top belt between the top two pulleys I suddenly noticed something that I did not notice in the daylight: There are four pulleys using one serpentine belt and the pulley directly below the alternator was not truning while the other three were spinning after starting the engine. That lower left pulley (as I stand at the front facing the driver) is the culprit and not the suspected alternator. Tighten down on the belt by leveraging the alternator tension and it simply made things worse for the lower pulley. Now I need to figure out what that lower left pulley does (AC?). By the way the lower left pulley does turn, just not as nice as the alternator. One a scale of 1 to 10 where 10 is cannot rotate it and 0 is effort less, the alternator gets 0.5 and the lwoer left pully gets about 8.5.------------- Thanks to both of you for your guidance and troubleshooting (both were really good ideas).