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Discussion Starter #1
Today I was driving home and on the highway I suddenly got a DSC message popping up and a message about the servo not beeing adjusted according to speed anymore. It got a lot more heavy on the wheel at low speed as well. It said I could continue driving so I drove 10km and did a quick stop to pick up my gf (with engine still running). I waited maybe 2-3 minutes there and then the "not charging" red message popped up. Limped home and parked it. Did a new test just to do diagnostics and then I got a SMG error message so I stopped the car to read up a bit on this case..



After reading up on it I decided to do some quick measurements with a oscilloscope according to the BMW manual (FUB-SOW-MCH1299SO1231) .

Engine just started - AC coupling not showing the DC voltage "properly" but it shows the AC-spikes from the alternator. These looks good according to BMW's specifications as far as I Can see. I don't think I can publish the examples from the BMW manual legally so I will not do that but it looks very similar to what I'm able to log.

Here after running it for a while with alternating loads. Still looks pretty similar and this is measured with DC-coupling so it shows the voltage below. Looks pretty normal to me.



Then the odd thing appears. After 20minutes and 27seconds idle I suddenly lost all AC-interference on the measurements and the voltage dropped to 12.5volts and a few minutes later it was down at 12.1volts. This indicates that the charger does not charge at all. According to the functional description of the charge system the alternator can reduce it's voltage until the alternator has cooled down again and it states that this is normal operation. However it does say REDUCE and not shut off so I assume this is not the case.



Does anyone got a tip for where to look and what to look for in this case? The high voltage registered in the DSC and SMG modules suggest that the voltage regulator has gone bad at some point but it looks fine on the measurements now. And since it completely stop charging after 20 minutes could it also be the alternator itself? Is there any other things I should look at or is this definitely a alternator/voltage regulator problem?
 

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The DME controls the alternator via the BSD bus based on input from the IBS. If the IBS data indicates to the DME that the battery is topped off and fully charged, the DME lowers alternator output to prevent overcharging and reduce countertorque therefore improving efficiency. So what you are describing with the reduction in DC voltage reading over time, makes sense to me and would probably correlate to a query of battery SOC (state of Charge) as to when the voltage tapers off.

Now, the AC component, agreed in any bridge rectified AC-DC converter, there will still be pulse ripple due to the zero crossing of the waveform, but the filter block of the regulator uses capacitors (opposing the change in voltage) to smooth that ripple out. While the shape and look of the ripple may look right, if I'm understanding your scope correctly, on a 1X probe at 1V/div, you are seeing nearly 0.5V ripple which seems *really* excessive knowing how sensitive the POS electrical system is in this car.

I would be wiling to bet your ripple voltage peak-to-peak value is proportional to current, indicating a failed component in the regulator and voltage drop across it is minimal with minimal current (I x R). As current goes up due to charging, voltage drop of the component goes up, therefore large output ripple P-P value.
 

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I concur. Seems like too much ripple. Perhaps I can put my scope on my healthy car and see what my ripple looks like. I can do that in between the plumbing job I have to complete tomorrow. It turns out my water heater circulation pump is less reliable than my m5.
 

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Discussion Starter #4 (Edited)
Thanks for the great description jcolley.Do you know if it's possible to pull any diagnostic data from the IBS sensor or the alternator itself over this BSD bus/diagnostic? Then I could actually see if it was the IBS sensor telling DME that the alternator should stop charging. In my eyes it should not tell the alternator to stop charing when the voltage is as low as 12V. I actually read out 11.5volts from the DME right before I powered off the car since I didn't want to break anything. That's very low for the control units. I guess the IBS could be failing to?

I will attach a screenshot of the BMW documents showing the "good" AC-ripple. Notice how this also has Voltage divider set to 1V and time at 1ms so that should be the same as my settings. I do agreed with you that the AC-ripple itself is really horrible but to me it looks like BMW states it should be like that. Will be interesting to see what rt7085 get from his working car.

You are correct regarding the ripple voltage increasing also. As I change the load the height of the pulses changes and with higher rpm the lenght between the pulses naturally changes due to speed of the alternator. It still doesn't look like the scope output where BMW states what component is broken tho.

rt7085 that would be really awesome! Comparing to a working car would give the best data.

Edit:
I should also mention that the RPM is not stable at idle. It's fluctuating between 1100rpm and 500rpm. When it is at a certain speed it's kind of stable there but it almost sounds like it's going to shut off when it goes as low as 500 sometimes. I didn't notice this before this electrical problem appeared. Can it be due to DME load balancing not working properly?
 

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The format of the BSD bus is something that remains a mystery. Somebody must know, but I do not. Maybe I will spend some time in the future reverse engineering it. Until then, no beef. Anybody have an old IBS sensor I can play with? I thinkable are all overestimating how complicated the BSD is. The alternator VR cannot be that smart.

BTW: If your idle is fluctutaing that much, is it just your cold start (cat heating) winding down from ~1100 rpm to ~700 rpm when the engine warms up? Or does is really go up and down that much all the time. If the latter is the case you may have other challenges ahead.
 

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Discussion Starter #6
Ok. I think I got some kind of serial mode on my scope. Think I can hook it up to rs232/uart,i2c and spi among others and log it. What that would tell tho will be a mystery to me :D It was just if there was some simple way of detecting the signals between the different components to see what was failing. If you are good with this stuff I could try to pull some info if you want.

I'm really mixed about what to use go for here as the alternator looks like it's working perfect until it suddenly cuts. I had the GoPro recording the screen of the scope for the 20minute session and it has a similar curve to the one posted above u til it instantly cuts so it's not going bad over time either. With a failing alternator I would guess what I would see low voltage or just some of the phases coming through the voltage regulator so we would miss a "top" in the readouts I did. The same goes for a messed up diode in the voltage regulator and a blown cap would prolly give bigger pikes and a lot less rounded curves. Here I'm just guessing tho.. When it goes off like this it almost looks like it's the temperature cut off or ibs saying there's no demand.

On my E70 I think the ibs show as a controls module and I know I can read out the amp usage, voltage and charge demand from it. I cannot find anything similar on the E60 prolly since its On that BSD bus..

Yeh just a coincident with the idle then I guess. Will order a new carbon canister anyways since I can hear some "air sounds" when opening the gas cap with the engine running. Prolly a good time to change this anyways. I was just thinking it could indicate a broken BSD bus or something like that if the DME didn't catch the message from ibs/alternator about the torque demand. I haven't read up to much on the DME functional description yet so I'm not familiar on how it handles change in loads like AC/alternator.. Guess now could be a good time doing so instead of guessing :)
 

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Discussion Starter #8
Great will order that also then.

Regarding this alternator what is the differences there? I can find many valeo and bosch alternators on autodeler.co.no but all look the same with different "angle". What should I get and what is the same as the stock one mounted there? From what I read in another thread value was the stock one also. I'd prefer to get the same valeo as stock mounted but since the cost is 1/3 of buying from dealership it would be great to order from some place like autodeler/rexbo or ebay..

Valeo:
VALEO Generator Automatisk girkasse for kjøretøy med automatisk klimakontroll med integrert regulator uten tilkobling for turtallsteller rotasjon med urviseren dobbel svingarm (439559) - 48 degrees
VALEO Generator Automatisk girkasse for kjøretøy med automatisk klimakontroll med integrert regulator uten tilkobling for turtallsteller med reimskive rotasjon med urviseren dobbel svingarm (437556) - 48 degrees
VALEO Generator Automatisk girkasse med integrert regulator uten tilkobling for turtallsteller med reimskive rotasjon med urviseren dobbel svingarm (437450) - 95 degrees
VALEO Generator Automatisk girkasse med integrert regulator uten tilkobling for turtallsteller rotasjon med urviseren dobbel svingarm (439485) - 47 degrees

Bosch:
BOSCH Generator for vekselstrømsgenerator aggregatrem (0 986 080 350) - 94 degrees
 

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Discussion Starter #9
I finally got around to order a new valeo generator. Will post back with the restults afterwards. Pulled out the stock one today and took a picture of the number in case anyone would need it for later ^^ It seems like I have some kind of early edition that is 180A and then they moved down to 170A later. The 7834160 number is the same but the "Ai02" ending is changed. When I search on ebay and similar I find a lot of "Ai03" with 170A so that must be some kind of upgraded alternator. I got the Valeo 170A so hope it works properly :)

The removal was super easy on this car. 1hour job and it's out and it wasn't even little space in there. I once pulled one from a Audio Allroad on that took 1 day to remove and 1 to install since the front almost had to come off to get enough space to get it out :D BMW Engineers have doen a great job here!

 

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Sorry never got around to putting my scope on the car this weekend. Spend my whole weekend plumbing. Hey, care to take the alternator apart and see how the BSD bus hooks into the circuitry? I would like to get some insight as to what IC they would use.
 

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Discussion Starter #11
Sure thing :) If it's a MCU inside there I can do a readout also if that can make any sense.

Btw I can feel a slight resistance when turning the alternator. Tempted to open and check the bearings if those are failing and making the alternator stop charing due to high heat. Not a big deal anyways since I'm replacing the whole thing but it would be funt to find the reason to why it broke down.
 

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Discussion Starter #12
I've then pulled things apart. At least the front bearing towards the pulley was broken. The rear one felt good. Can't see anything obvious on the winding's but I didn't measure them either to be sure. I assume those are good since it works for the fist 20 minutes. My best guess is that the bearing together with motor heat is causing heat to go over the limit for the alternator to cut charging but I'm no mechanic ^^

I'm not sure how to attack that voltage regulator. I attached some pictures showing it here but If I open it more than this I will for sure break something. It's completely sealed off. Any advice on how to continue?
 

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Oh my. That looks like a flip chip naked die, bonded out to the over-molded conductor frame. That is as raw as get get! There is no information there for sure. Too bad.

BTW: That alternator looks like hell indeed. The bearings rusted. Norway is a tough place I guess. Is it parked outside?
 

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Discussion Starter #14
In my ownership it's parked inside and I very rarely drive it when it rains :p This is my third car so it's not a daily.

But this is most likely the stock alternator so it's 12 years old.. The bearing that was rusty felt perfect actually. The problem bearing was the one towards the pulley and it didn't look rusty. It wasn't locked either but I guess that it could make problems once heated up properly. Anyways it always feels great when I know I chang a broken part and I was battling myself wether to order just the regulator or they whole thing. Glad I choose to order the whole alternator when I noticed the condition this was in.

This BSD bus is there any info about it in the BMW system? I'm tempted shooting valeo an email asking if it's possible to get the bus specification and protocol. Can't be that big of a secret since there is so many making these alternators?
 

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Yeah. Great work. I think the humidity in the (salty) air is a big factor as well. The M5 is quite sealed off with all the bottom covers. From the front there is two radiators to penetrate and a fan cowl. I sometimes see pictures of M5 engine block down south on the US and there is barely any corrosion. Unlike mine. Here in the northeast it is a bit salty. And I drive it every day summer and winter. Hey, I get to enjoy it every day! And driving it every day is good for the car.

Valeo is likely not to give it up; But definitely try. I work with silicon Manufacturer and have strong relationships. But they keep it close, for good reasons. I was taking the route of searching patents online. Sometimes these parents are the eminent resource for information. I will keep looking.
 

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if you look under a loose or microscope at the die, is there a IC manufacturers logo or brandname on it. Think of Infineon, ST Microelectronics, NXP or the like. This could be an interesting lead on where to go look for information on the mystery BSD bus.
 

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Discussion Starter #19
Even if there was I'd have no chance of hooking up my microcontroller programmer to this as the connectors will be way to small. I can try to remove some of the goop that is over the controller and have a look at it. But I suspect that it's really primitive. They don't even have a signal to DME to tell why it stopped charging (overheated as an example) so I wonder what info is passed there at all ^^
 

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The DME is also hooked up to the BSD. So, whatever the alternator gets, the DME gets as well. I am just asking for a chip logo to help my search for information. When I know the manufacturer of the chip, this may provide extra hints as to where to search. I have spare DME in my garage, so I will look today what kind of transceiver might be on that side.

My hunch is that this BSD signal is a composite signal of PWM and some basic status information bytes, kind if like a LIN bus. The IBS does sample the voltage, current and terminal temperature and send it to the DME. The DME make decisions on how to drive the alternator. Here is some information I found on the PICO scope site that might support this idea:

https://www.picoauto.com/library/case-studies/2003-bmw-5-series-4-4-v8-communication-error

It says nothing about the bus format at all. They turned on LIN decoding but of course they have no clue if thesis even correct. I also found this, which i also marginally useful, but it tells us a little more:

http://www.shrani.si/f/3d/3J/BP0gtSu/1/e90-voltage-supply--bus-.pdf
 
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