Alternator
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noticed in park that alternator pulley was rotating slow (other pulleys fine, at that time) and have occasionally started experiencing front lights dimming when coming to a stop.


wondering bout alternators,

could the alternator itself cause its pulley to rotate slower?



appreciate any info to share about alternators

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Belt Tensioner


1.


Seen posts saying use acdelco o-rings ACDELCO Part # 1534066 More Info {#25537068} for the 47065hp alluminum elbows.
rock auto lists a different ac delco o-rings ACDELCO Part # 24502846 under buick le sabre 2000.

which o-ring for my car?



2.

A - Just want to make sure, but no doubt these elbows can be put into place without taking off the plenum,etc ?

B - Does the coolant reservoir need to be taking off to get the bolts off the tensioner?


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First thing to check with dimming lights at idle would be your electrical connections. Make sure all of your battery connections are clean and tight. Disconnect them, take a wire brush and clean the white corrosion off.

If that doesn't solve it, question is, how old is the battery? If its pretty old and maybe an elcheapo, maybe time to replace it.

Or, the usual culprit is, if its the original alternator, its probably getting weak and cannot support enough voltage at idle. Its probably on its way out also.


Coolant elbows must be installed while the lower intake manifold is removed OR the belt tensioner removed.

BUT. If the lower intake gaskets are 2000, then I highly suggest upgrading those to the better ones when you replace the o-rings and elbows.

LIM gaskets and battery - both 2 years old,
autozone duralast battery -$100.
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it just seems odd the elbows can be taken off when taking off the belt tensioner,,
like there'd be some thing keeping it stuck where it connect to the LIM and coolant hose



1.

so a poor operating alternator can cause the pulley to spin less ?

i figured if alt-pulley was spinning bad it would be the pulley bearing/part or some other pulley interfering on the belt

Maybe I misspoke or didn't speak enough. LOL

Yes, the coolant elbow between the belt tensioner and LIM can be removed while removing the tensioner.

I don't know what you mean by spin less? I do know that an old worn out (pending failure) alternator can't produce enough energy while the engine is at idle. But can produce normal energy at a higher RPM.

nothing holds the elbows it thats one reason they leak all the time. i haven't had any leaks with the orings that came on the aluminum elbows, i put them on my inlaws 00 lesabre and my bonnie. just make sure all the little plastic pieces get picked out of the holes and i use a little back rtv on the oring area when i put it together.

by spin less....not rotating quick and fast like it should,
the alt pulley rotated slow, while the crank/water/belt pulleys rotate quick




what im trying to ask is can the alternator (its inner parts) cause its pulley to rotate less?


trying to distinguish between only the pulley going bad and giving the alternator a hard time versus just the alternator



like, hey , instead of replacing the whole belt tensioner just replace the tensioner pulley


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when the dimming of front lights had occured it would happen when slowing down from a higher speed.
so 40mph then slowing down (15mph - dim) (5mph -dim) to idle 0

I think its just a visual effect of some pulleys being bigger vs smaller and how fast they rotate in relation to others.

If your lights are dimming at idle, but brighten when the engine RPM goes higher, more than likely your alternator or battery is on its way out.

"by spin less....not rotating quick and fast like it should,
the alt pulley rotated slow, while the crank/water/belt pulleys rotate quick..."

It'* a serp belt.....the belt moves at the same speed on all pulleys......the alternator pulley being smaller than the crank pulley has to spin faster....

GM came out with a TSB about this, for all vehicles......it showed the output of the alternator as rpms'* drop as the engine warms up.....the output can drop to around 80%....rpm'* at idle on a cold engine are higher than rpm'* at idle on a warm engine......lower rpm'* translate to lower output......

So it is considered "normal", depending on the load on the system, for lights to dim when coming to a stop.....for example, in the winter time, you may have the defroster on high blower speed, the rear defogger on, radio on, lights on.....now you come to a stop, and those rpm'* drop, and the load on the system will make the headlights, dash lights dim, somewhat.....

Of course other things contribute to that dimness......bad connections, weak battery, bad belt, bad tensioner, bad alternator, etc.

In the "old days", output was controlled by the voltage regulator in the alternator, alone......the newer cars have become more sophisticated....we have current sensors on the battery cable providing input to the PCM, which now controls the voltage regulator....which kind of complicates diagnosis if you don't have a scan tool....it'* rare but I have run into a couple cases where, the alternator was replaced several times, and the problem was a PCM....

The o-rings on the aluminum coolant elbow should be fine, I'd only recommend getting the AC Delco O-rings if you went with the old plastic coolant elbows, which I do not recommend going with.

Gus, well said "lower rpm'* translate to lower output", I have did a little research in the past, because my lights have always slightly dimmed after I have been driving a bit, and come to a stop, from what I read that is normal, unless they are dimming a lot more than they ever have in the past, then it may be the other causes mentioned.
It does sound like it may be one of the other possible causes though, as they said "occasionally started experiencing front lights dimming when coming to a stop.".

either way if it is high or low output...the alternator pulley will always spin faster than the crank.
my alt pulley rotates slower than the crank pulley.



anyone got that GM tech bulletin ?