Please, do you agree with me or not. Your response is a bit ambiguous.
I say the alternator or the voltage regulator is faulty.
Slipping belts make noises easily heard.

 

Thanks 'yall, for the ideas. The belt is not slipping and is quiet, the tensioner has not been replaced lately, however, the voltage output would simply fall off to somewhere near 12.7,at RPM's above 2500 and when the RPM's fell back below that number, the voltage would "hop" right back up to around 14."something". We just took it off and put it back in the box and are condemning the internal voltage regulator component of the alternator as faulty.
Thanks again....Peace

 

I totally agree. While I suppose checking belt tension is a good idea, I've already had an alternator that did not want to charge above a certain RPM. (Can't remember what RPM...)

 

Are the component parts of the 120A Valeo alternator listed here on the forum somewhere so I might attempt a rebuild?

 

There is such a list, I'll see if it has the parts listed.
What is the Valeo part number?

 

Thank you kind sir, the numbers I got off of this Valeo are as follows: (large numbers) A 112 154 02 02, underneath that is a set of numbers reading - Q1 120A 14V, and also a small set of numbers reading - SG 12B 06Q , 254 257 2A, 404000097 and 18/04.
I understand that unsoldering the regulator is part of this rebuild procedure when replacing the bearings. I'll go check out youtube videos to see if someone has posted this operation....Peace

 

These are the Valeo alternators and the parts are listed.
The SRT is the bottom one, the parts for it are listed.

 

I see the bearing sizes are not listed, so I suppose I will have to remove them and mike em to match.
....By the way, I have a plant record for pushing stationery envelopes through a press, 60,000, 2-color, return-flap type envelopes to be exact in one shift...ha ha..so when I read that under your name, it has a special connection...Peace

 

Quite the coincidence then about the envelopes.

 

Rather than starting a new thread I thought I would ask my question on my battery light issue here...

My battery light is on. Turning the key to on, but not starting, the battery was reading 11.69 volts. With engine running the alternator is putting out 13.78 +/- volts at 2500 RPM. So I assume the battery was shot so I replaced it.

Battery light is still on. When I pulled the engine cover off the right side over the alternator was very warm but the rest of the cover was not. There is a faint electrical or over heating smell coming from the alternator area. When I touched the alternator with a rag between it and my hand it was extremely hot.

Do I assume that even though the alternator is producing the normal charging volts per above that there is some other issue with it; bad bearing or some other alt component that is over heating and REPLACE the alt? Or are there any other reasons that the battery light would be still on after replacing the battery?

 

The alternators do get hot, but an electrical smell is not normal.
Check all the cables real good for integrity and good connections, with negative terminal off the battery, check the ohm reading from the big post on the alternator to the + battery terminal, should be close to 0 ohms.
If everything checks out, I guess the alternator is the next step.
( does it spin freely with the belt off ? )

 

Thanks for your assistance!

Ohm was 0, all wiring looks fine.

I can barely move the belt tensioner to remove the belt, assume that if I am facing the front of the engine that the tensioner needs to be rotated counter clockwise to remove the belt...have not replaced the belt before only 23,500 mi. and it looks fine. I will revisit in the AM and try with a longer breaker bar.

 

A HOT alternator means one of TWO things:

1) Bearing or other failure, causing friction - friction means heat.
2) Far too much current is flowing - this would be due to low resistance between the alternator output and ground - this is commonly called a "short circuit" - but I don't use that term.

Since the light is on , it implies the alternator is not charging, but this may or may not be the case. Your voltage readings imply an issue. At 2500 RPM on the engine, the alternator should be able to sustain 14.2 or more volts. But if there was current flowing, it would drain the battery quickly once you let the car sit. That amount of current would take the battery down in way less than, say, the usual 16 hours the car may sit if it is a daily driver.

The battery light circuit is rather simple - given all the indications, and not being there to verify for myself, I'd say the alternator is bad. If you change the and the light does not go out, then I am wrong.

At NAPA, you can pick up a rebuilt unit for $220 or so. Sounds like a lot of money to prove me right or wrong, but I don't know what else you can do.

 

Update...got the belt off, disconnected the two electrical connections and removed the two bolts. But, the alternator does not budge. it appears there are sleeves/spacers in the front mounting bracket bolt holes that are holding the alternator in place. Any suggestions how to get these sleeves out enough to allow the alternator to be removed? Just did a search and it appears that the alternator needs to be pulled towards the front of the car; that must push the sleeves forward far enough in the bracket to free the alternator. I will try this tomorrow after work...

 

Exactly right.

 

Move the alternator forward WITH the bolts loosely in place, you do not want it falling out and damaging the cables to it. A little WD40 on the bushes and left for a while may make it easier. The alternator is pinched between the bushes, the rear location and the bolt head. The bushes stay real close even with the bolt loosened.
Grease the bushes before assembly, it might make it easier for you if you have to do it again.

 

Thanks for the suggestion...I was able to get the alternator out this evening with a little assistance of a flat pry bar.

My next question...is it worth trying to see if it can be repaired? There is a Starter & Alternator shop not far from where I live. The bearings seem to be fine as there never was any whining and spins freely off the car. Since the voltage regulator can be replaced and it was not putting out sufficient voltage it may be the culprit. OR should I just bite the bullet and replace it?

 

What brand is it? Bosch or Valeo? $25 ,for a Bosch regulator, takes about 10 mins.

 

It is a Valeo A 011 154 64 02

 

It is a Valeo, but that is the Mercedes part number for that alternator.