Question about alternator

[90turbo1]

Ok, Alternators have been beat to death but this question I cannot find in search.

my sons car 2004 325xi. manual trans. nav, heated seats. the alternator light was flashing on dash. random times and now just stays on. I checked the battery ok, checked connections to jump start and battery ok. removed air box and found B+ connection at battery is loose and was arking and sparking pretty badly to the point it burnt up the nut and washer. The alternator has a rebuild sticker on it but no other markings that I can see. Previous owner installed it before we purchased it.

My first question is. How do I determine which alternator it takes? Valeo or Bosch, it has the air duct. I am assuming its a 120 amp. when I look at real oem it comes up with either valeo or bosch as options and valeo says "ended" in description.

So am I to assume the Bosch is the replacement. When I worked at the dealership we had to specify valeo or bosch to the parts dept.

Also next question. BMW calls the nut on back for B+ an adjusting nut. What is the thread pitch of this nut? The head is 17mm plastic, the rebuilt had a regular nut and lock washer installled which is burnt up pretty good.

thanks

[MarcoZandrini]

The only real way to determine which brand of alternator is in the car is to read the label on the back of it. You'll need a flashlight and a mirror. Remove the air filter box and the upper intake hose. I recommend that you go through the car to clean and tighten every grounding point. A critical ground is located at the bottom front of the engine on the exhaust side of the engine compartment. The main engine ground is located there.

[90turbo1]

The only real way to determine which brand of alternator is in the car is to read the label on the back of it. You'll need a flashlight and a mirror. Remove the air filter box and the upper intake hose. I recommend that you go through the car to clean and tighten every grounding point. A critical ground is located at the bottom front of the engine on the exhaust side of the engine compartment. The main engine ground is located there.

i see you didnt read what I posted......

[randy72877]

The alternator information is PRINTED on the back of the alternator (the plastic cover that the cooling duct connects to) you should be able to read it with a mirror. If not it's possible that it was removed in the cleaning part of the rebuilding process. You can try to match it to pictures on parts websites or try to identify it through the number on the rebuilding label.

Sent from my SAMSUNG-SM-G870A using Tapatalk

[90turbo1]

see that is where I am asking the question, there is NO indentification on back of this alternator. and from what I can tell is the valeo is discontinued and bosch is the replacement. There is no real difference in swapping the two as far as I can tell and from what other techs (yes other BMW techs) I have talked to state. I was just wondering if there was a way to determine what one it should have been fitted with.

Also i tried to match the part number sticker from rebuilder and come up with dead ends. I have no idea where they purchased it from or such. or even if its from a parts store.

oh well

[Eaglesail]

Would it give any reference to you for which regulator fits..which? I know it's a dumb question, but what parts build each of either alternator? ...kinda like 'reverse engineering!

[90turbo1]

ok, so I purchased a new nut for the back of the alternator (called an adjusting nut in parts catalog) wouldn't thread on. cleaned the B+ cable connection and yes checked the grounds. no luck threads are too messed up on back from the arcing and sparking to fix. metal is super brittle now also. removed alternator and removed voltage regulator. Apparently Valeo and Bosch use same regulator. removed regulator and the stud is simply a metric bolt but..... you cannot remove the bolt without first un-soldering the diode trio and then removing the trio from the alternator. it sticks up from the bottom and is held in place by plastic. So before I get a different alternator I will try that.

I will post some pics as I did a google search and this comes up often along with burnt b+ cables from alternator.

[MarcoZandrini]

Bosch and Valeo used different voltage regulators (VR) as far as I've heard. I had to replace the VR in my car. It has a Bosch alternator. Ordered the VR from fcpeuro and it's labeled "Bosch." You may be correct though as I wonder if Bosch actually makes the VR.

[TonyAngel]

Do the two alternators look the same? I mean, are there physical characteristics that would allow you to distinguish the two? If so, do a google search for you model car with the word alternator in it and click on the "images" tab.

[90turbo1]

Do the two alternators look the same? I mean, are there physical characteristics that would allow you to distinguish the two? If so, do a google search for you model car with the word alternator in it and click on the "images" tab.

xternally they look the same. the rear air inlet cover, connects to lower duct work is perfectly smooth on rear. no stamping, stickers nothing. the regulator has no markings or numbers on it. best I can make out is its a bosch, the valeo regulator is slightly different in shape. but I have been told they can be swapped also. who knows. the valeo is no longer available through bmw though. And from what I can tell doesnt make a difference if the car came with valeo or bosch you can swap the two but you SHOULD NOT swap to a different amperage.

Mine does have a B+ #1 and B+ #2 terminals on the back. M8x1.25 studs. the B+ #1 is longer and bolts through a magnet (i am thinking a noise suppressor) on the rear cover, B+ #2 is a short stud. both are power outputs but I wonder what the #2 terminal was used for?? europe diesels? who knows..

When I searched for pictures online most bosch pictures only show one terminal as well as valeo.

[MarcoZandrini]

The connectors at the rear of the alternator are different. The Bosch alternator gas a rectangular connectircwhile the Valeo has an oval connector.