Battery light on. How to identify alternator model/brand?
 

I think the alternator or the starter are going bad. I have ruled out the battery as I took the battery to the Batteries Plus and they confirmed it is still good.

I tried viewing the voltage through the cluster but I wasn't able to get to the option.

For now I am just trying to figure out what type of alternator I have to see what the cost of refurbishing it myself or replacing it could be. Is there a way to figure out the model/brand alternator without taking it out? I've had this car for 20 years now but I can't recall if this is the original alternator or not... Lol

Wondering if I should do the oil housing gasket too while I am in there.

Most likely you have a Valeo alternator. You can get an inspection mirror and see if you can read the name.

I switched mine from Valeo to Bosch when I replaced mine about two months ago. Turns out I could have probably just cleaned the brushes.

I refurbished wife's in the past year by just replacing brushes and swapping polarity of the slip rings (since only the one polarity takes 3/4 or more of the wear I didn't even bother changing the slip rings this time).

If you get some brushes and follow my thread how to swap the polarity you can probably get 60-100,000 more miles.

Thanks gents. I did not get a chance to get the splash guard and all that other stuff out of the way so I did not get to use the mirror to check the brand, but thanks for the photo, now I know what to look for!

I was however able to get the cluster tests to work. With engine OFF, test #9 says 116, which I assume means 11.6volts. With the engine ON, test #9 says 111 (or 11.1v).

The battery was fully charged 2 weeks ago and the car had been sitting in the garage without me messing with it for 2 weeks and I can't believe it has discharged the battery that much just sitting there. :-)

Now that the test showed me the low voltage while running, I am going to assume that means that alternator is bad and so will spend some time tomorrow removing the alternator.

If the alternator is only putting out 11.1 volts running I'm surprised it runs. I wouldn't trust a battery test in a auto parts store. I've taken batteries in that would not charge that my battery charger said were bad and they tested ok in the parts store. You definitely have a bad alternator. Put in a new one and put the battery on a charger for 24 hours. After charging for 24 hours put a voltmeter on it and see what the battery is holding. If it's not holding 12.3 volts it may be bad as well.

Or just remove the voltage regulator is situ without removing the alternator. Then renew just the brushes (or the regulator with brushes).

That sounds like a lot less work! I am gonna try that for a little and see if I can figure out how to do that. Thanks!

That is correct. Definitely alternator.

You’d have to have at least one extra joint in your fingers to remove the VR in place. I wanted to do that very badly.

Heres a tip though: the most difficult part is getting the bolts back in; grind the end into a cone.

I've redone mine and wife's and it was just brushes. I even replaced mine when it failed to find out the bushes only needed to be cleaned so now I have a spare alternator.

The trick to reinstalling the alt easily onto the bracket is to refit the long mounting bolt (on the bench). Spray it with penetrating oil and lightly whack the bolt head a few times with a deadblow/rubber hammer. This moves the sliding nut back a few mm and is easily refitted. The captive nut is made to slide. Don't get carried away, a few light taps are all you need.

Also, there are at least two different Valeo alts depending on the options/packages, maybe 100amp and 140 amp. If you have heated seats, you def have a 140amp.

That's a great tip about the captive nut. I thought it was just a threaded hole in there block.


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I've also used a giant socket on the outside end of the ear and pulled it; but the mallet works just as well. I do this with the ear supported from the back also with a large socket, so theres no risk of breaking the ear off.

:thumbup:
My 2001 3.0i has a Valeo 120A. Good tip on figuring out the amp rating as well as Bosch-vs.-Valeo.
Attachment 78783

The plastic housing on the back side of the alternator does not have any markings besides the B+ and B-. I am also unable to see how to remove that housing to even attempt access to the regulator, so I am just gonna remove the whole thing.

Now, to remove the alternator, I guess I need to remove the fan shroud and radiator fan too? Otherwise I don't see how I can get clearance to move the tensioner pulley to losen the belt. I see I need a T50 male socket to move it and the socket alone is like 1.5 inches long so I can't fit the breaker bar nor ratchet without removing the fan. :-(

@oldskewel: thanks for that photo. I was trying to do this all from above, so I have not looked underneath yet. Maybe there's a sticker on the underside of the unit... will check, right after lunch. :-)

I you replace the alternator, time to replace the OFH Gasket as well.
I posted the photos in forum.

I stuffed my phone down there and took a whole bunch of blind pics; my white label was still intact, so it was easy to tell from one of the 20 random pics I got.

Been a while since I replaced mine, but yes you need to detension and remove the belt. First, remove the shroud fasteners at the top and but leave the shroud in place. Then remove the fan clutch (it's reverse threaded) from the water pump snout and remove the fan/clutch and shroud together; do not bang it into the back side of the radiator. Do the same sandwich on reassembly. To make alt removal easier, loosen the long bolt 3 or 4 turns, then whack it gently as indicated above; makes removal from the OFH bracket sooooo much easier.

I remove/replace my alternator from the back. To do this I remove all the intake hardware from the snorkel through the intake boot and the DISA,also the aux coolant pump I disconnect the attached point so I can move that around to make more room. It will fit mostly straight up once moved maybe 20 cm aft.

Not sure on E53 but at least on E46 and E39 with M54 engine this can be done in situ. (Also done it on my E53 but with M57N engine.)

For example this video shows what you are looking for to remove the back cover and then change the brushes.

https://www.youtube.com/watch?v=aVvPzwtxdrM&t=25s

I pretty much always do stuff from above, and am sure I did it from above for the alternator. My alternator (120A Valeo) looks EXACTLY like @upallnight's pic in post #2 - with the "Valeo" cast in the middle just like that. Since you don't see that, maybe it is encrusted in oily dirt or maybe it is missing and you have a Bosch.

I don't know the numbers, but one clear difference between Bosch and Valeo is the pulley diameter. But probably easier to just pull out the alternator.

I agree on doing the OFHG while you are in there.

I can't remember on fan removal. I've now removed and replaced that thing enough times that I barely think about it. BUT, if it is your first time on that, don't underestimate that step. If the previous person torqued it on there, it may need special tools to remove it. If not, you just need a 1-1/4" open end wrench (slightly tighter, at 1-1/4"=31.75mm than the 32mm spec wrench would be, so it transmits the impact a little better) and know how to hit it just right. I bought the special pulley holding tool for the first time I ever removed it, and have not used it since.

Also, on diagnosis ...
if your voltage readings (that you are not sure about) are correct, then yes, that is a clear indication of a charging problem.
And a charging problem is *probably* caused by the alternator (but could be other things)
And if it's a problem with the alternator, depending on mileage, it is probably as simple as worn brushes, which are part of the voltage regulator. If you get that far and don't want to replace the whole alternator, just replacing the VR or the brushes may be a cheaper solution.

The Bosch and Valeo will be interchangeable as a complete unit, including VR and pulley. But the individual components of the Bosch vs. Valeo assemblies will not be interchangeable. E.g., Bosch VR will not work on a Valeo alt.

I just found some links I saved. First one is a thread from when my alternator went out. Many photos. The other xoutpost thread shows many pics and a tutorial for the Bosch. Maybe seeing those photos of the Bosch and the Valeo will help you decide which one of those two options yours looks more like.

https://xoutpost.com/bmw-sav-forums/...3-0i-01-a.html

https://xoutpost.com/bmw-sav-forums/...-pictures.html

https://www.bimmerfest.com/threads/d...ebuild.516680/

https://www.bimmerfest.com/threads/v...eplace.514504/

I watched that guy's great videos. Very interesting and impressive. I even bought the full rebuild kit (brushes, slip rings, bearings) from him on eBay. Ships from Ireland, so not good if you are in a rush. I think I did a quick VR swap when my alternator failed, and then bought his kit, and then when I had the engine apart later, it was convenient, so I did the rebuild.

Actually, looking through the video just now, I'll say that the back cover, etc. all look completely different vs. what mine does. Once you get deeper in there for the rebuild, everything he says applies, and the video is good. Apparently Valeo used the same brushes and slip rings on every alternator they made for about 3 decades (don't quote me on that, but I wish other manufacturers did not reinvent the wheel as much as they do).

And I won't doubt that *you* can do it in-situ, and if I really needed to do it to win a bet, I could probably do it too. But given a choice, and knowing what I know so far, I would remove the alternator.

On the tightness of the alternator when reinstalling, I've just cleaned up all the surfaces, and use anti-seize on a few key spots, and have never found it to be a big problem - e.g., no machining required. But I'll also say that probably due to being in California, I tend to have a lot less corrosion on everything vs. most of the photos I see of other engines.

Thanks all! You are all fantastic, you've all helped me a lot!

I went ahead and removed the alternator. I was able to release the tension on the tensioner pulley without having to remove the shroud and radiator fan, so that was welcome! I have the tool to remove that fan and I have done it a few times, but I honestly hate doing that. :-). Oh, and I was wrong on needing to use the T50. There is a welded nut on the bracket of the tensioner that I had not noticed (obstructed by the belt) which is what I was supposed to be using to move it. :-)

This is likely a cheap aftermarket unit because there are zero brandings on it! Zilch... Not even numbers or symbols on the metal. The plastic looks identical to the Bosch 120 model (with that little black plastic cover that is hiding a bolt next to the positive terminal. I don't remember replacing this alternator but then again I've had this car for 20 years and my records and memory aren't that good...

I compared the alternator to those in the photos in the posts recommended by @oldskewel and it is definitely NOT a Valeo.

I removed the plastic backing and it was super clean inside, not full of debris and dead insects like in one of those photos. Lol...

Anyhow, the voltage regulator screws were in REALLY tight. I had to use my impact to get them out. The regulator does have some numbers on it and doing a search on google, it seems those numbers match an aftermarket replacement for the Bosch voltage regulator. The images google shows for the Bosch regulator look identical to this one, minus the bosch logo and part number...

I think the brushes on the voltage regulator are ok though because they are only about 1/32" in size difference from each other and the brushes exert pressure when trying to mount the regulator back on.

So, I am tempted to just get a new alternator and call it a day. I see FCP Euro has the Valeo 140 Amps for $222...

Maybe to rule out a wiring issue external to the alternator, you could reassemble it and have it bench tested at PepBoys, etc. Hopefully it fails, to confirm you conclusion. Not much to lose other than the effort to do that.

I'd do the same thing in your case - just get a complete replacement. So much uncertainty for something with no brands on it - not worth the time to try to rebuild it.

BTW, I have seen this before - a part-by-part Chinese no-brand clone of an alternator - Bosch in this case, it seems. The benefit to that is that parts may be interchangeable with real Bosch ones. So if your replacement were a Bosch, and you like keeping old parts around, that dead one may prove useful one day.

Ah... Good idea to get it bench tested. I will put it back together, it should not take more than 5 mins. I think there's a Pepboys around here.

Yeah. I hope it fails the tests too! :-). Thanks!

Absolutely bench test even new / rebuilt.

Replaced doesn't mean fixed.

That looks like a crap alternator and you have a couple of fried diodes so you are going to need a replacement.

I received the replacement alternator and installed it. All good now! I can see the test voltage while running being 13.4 volts.

One interesting thing: I did take the new and old alternators to 3 different places for bench testing: O'reilly, AutoZone and Pep Boys. Only O'Reilly had the machine that supported either of the alternators. The O'Reilly's said that the old alternator was good, so I took it to a different O'reilly's just for kicks, and they said the same... :dunno:

Anyway, whatever, I have a new one on there now.

13.4 is kind of low. I think you should typically be seeing 13.7 on the low end with 14.1 on the high end. What brand did you buy? Is it new or a rebuild?

13.4 is fine depends on where you measure and how soon after the battery was pulled down from starting.

Disagree. If that was the running voltage he's talking about, it's what is being produced by the alternator, not what's in the battery. I read it as the running voltage. It should be higher in a new alternator.

When I recently replaced my alternator it took about 10 miles is driving before the voltage broke 13.0.

The alternator is perfectly fine and I suspect I will see 13.6-13.8 if I monitor it with OBC today.

Once the battery is fully charged I would expect to see as high as 13.8. I've never measured above 14 on a car that didn't have a problem.

The voltage regulator has temperature compensation so you might see 14 volts on a hot day as the internal resistance of the battery gets higher and higher voltage is needed to achieve a full charge. This is all assuming voltages accurately measured at the battery NOT the OBC or scan tool. I would say the OP has his problem fixed and shouldn't be looking further unless it's just to learn more.

Hi gents, thanks for the observations. I am learning from you all.

I saw the 13.4 when I first turned on the car and as it idled for a few seconds. That's all I had observed. But now that you guys informed me that 13.4 is on the low end, I have taken the time to observe it further.

So, my observations are:

• Voltage: starts at 13.4 after about 3 seconds from cold start, and while in Park for at least first 30 seconds (not sure if it climbs or stays there if it stays in park for a while)
• Voltage: 13.4 while reversing from park
• Voltage: 13.6/13.7 while driving at around 20 miles per hour
• Voltage: 13.7 while driving at higher speeds than 20 miles/hr

The alternator is a new Bosch 140 amp unit. Well, it is supposed to be new, at least according to FCP Euro. But I am not certain because the box is a retail Bosch box nicely sealed, but the unit has a Bosch sticker, but the plastic part says Valeo... I am reaching out to FCP Euro to check.

Thanks!

Which is exactly inline with expectations. Also good on the 140 Bosch. Same I did. I picked Bosch over Valeo as the VR is 1/3 the price.

I did get a lifetime warranty with O'Reilly but I might be stuck in a town without an O'Reilly at some point and it'd be a great perk to have a $35 fix one day vs $250.

Ah... Yeah, it is a remanufactured one... It did look really nicely cleaned up though, even the coil windings. Hopefully it lasts. :-)

Wow, that's a shocker on the Bosch / Valeo hybrid you've got. Let us know what the answer is. Am sure it's OK, but still weird.

On the voltage, as was said earlier, it matters where you measure it. A voltmeter measuring at the B+ jump port in the engine bay will give you pretty close to exact alternator B+ voltage.

Measure anywhere other than that point, and voltage will be lower. I think I remember noticing the built-in high cluster internal test showing consistently up to half a volt lower than the true alternator voltage.

You'd get similar results if using one of those voltage gauges that plug into the 12V outlet.

The electronics like to have regulated voltage, and generally regulating voltage (for stability and control) means reducing it a little.

My guess is that things are fine with the new alternator, and that you have solved your problem. But it is a little concerning that the store did not confirm your old alternator as bad. Those tests are always a little suspect. It could be that you have an intermittent problem - diode conducting or not, for example - that somehow temporarily fixed itself during the removal, disassembly and reassembly.

The usual suspect of bad alternator is the combination of loss of spring pressure on the brush and enough debris or enamel buildup on the slip ring. Just a good bump the right way and you can probably get another 1000 miles.

When I removed mine I discovered it failed from brush dust buildup it just needed a cleaning. However I already bought the new one so I'm keeping the old one as an emergency spare I do have two e53.

Anybody within a couple hours drive of me could take advantage of the spare should it come in helpful.