It will most likely be the voltage regulator. They can fail in strange ways. Have the generator tested. It should put out around 70-80V AC on each phase. A new regulator should fix any other output issues.

If the output is nudging 16V its too high and the only way that can happen is with a faulty reg/rec unit.

 

+1 for the VR being the most likely candidate , had mine changed last year , from memory it was about £50

 

I forgot to say, I only have one fault code regarding anything related to alternator (I believe) : 44E2 - Generator. No further informations. If I erase it when engine is switched off, it will stay away, until I start the car, and then immediately it pops its ugly nose out. I've had it for as long as I've been able to scan the car with INPA (basically since May from last year).

This morning I did my usual trip to work, again, with 11.7. Stayed around 11.7-11.6 (and some surges to 12v) for ~10 mins and like I said in first post, gradually went to 15.1-15.2. This time I didn't turn any accessory on, just in case. Still started to fluctuate, although not as violently as usual.

So, regulator you say ? I think i'll try that route.

 

Have you tried disconnecting the IBS, it could be failing with parasitic drain like drops at times.

 

I had voltage issues on my e60 and I changed the voltage regulator on the a.ternator. It's a fairly straight forward job and it sorted the voltage issues out and much cheaper and easier than changing the alternator.
Cheers
Jim

 

But would it cause a battery to eventually die ? The question may sound silly and the answer pretty obvious, but i'm just trying to be as sure as possible before buying anything.

 

Your symptoms sound very similar to mine , at one stage my battery did flatten , I took the alternator off and dropped to my auto electrics guy who tested and confirmed vr

 

Wonky regulator would be cruel to the battery, eventually it'd quit

If you think about it, you are seeing wildly fluctuating voltages for no apparent reason, so regulator may be part of the scheme, but there could be reasons why, like poor connections at various stages, current flavour of the day is the thing reported on Watchdog/BBC News and others, the rear of main fuse panel connection not being up to the job, if the regulator detects an odd situation it's response might be part of the pattern you're seeing.

I got one of those ciggy lighter battery voltage monitors things - the one I got had dual USB ports, that was around 15 quid, but they start at under a fiver, that may give a less obtrusive view.
https://www.amazon.co.uk/Cigarette-Lighter-Voltage-Voltmeter-BuyinCoins/dp/B0092KVYGI is similar, in my case it reinforced the battery was on the way out.

Regulator sounds good, but the other view might be you haven't got enough information, 15.9V sounds way high for 'normal' - though I'll keep an eye on mine - was kinda nice just having it there.

 

The 15.9 thing was a long time ago though, now it doesn't happen anymore. I almost wish it did, at least at the time, I had a solid 15.5-15.9 voltage.

My current biggest trouble is the slow escalation and then fluctuation, starting every morning from 11.7-11.8 and then acting funny, and feeling like it's a scripted fault, "scheduled" as I said. That's the thing that makes me hesitates the most. The way I see it, is that a faulty reg would always mess with voltage, rather than gradually eff things up.

But then again, I know very little about how an alternator works, and even less about voltage regs.

 

<12V is low. A regulator is really only a semiconductor switch. If you consider it sits in a fairly harsh environment and gets exposed to quite an extreme range of temperatures its not too surprising they fail. Plus you have a bunch of diodes in the circuit to convert the A/C to D/C and they are also known to fail. The generator itself ought to be fairly robust but a faulty reg/rec can cause additional heat build-up in the stator.

Get the thing looked at. They are relatively easy and cheap to fix.

 

I will.

Just one more last question : what are you guys reading on your vehicle(s) (through hidden menu/voltmeter) ?

I'm curious to know what are the measures of a fully fonctionnal regulator.

 

I've just replaced the regulator. Luckily it is indeed a straight forward job as mentionned on previous page. In fact, the only hesitation I had was about the plastic round top that covers the brushes, as I wondered whether or not I should pop it out. I'll post pictures of the worn brushes, just for the curious out there but they were really worn out, in fact, I doubt they actually made contact with the slip ring/rod/rotor/whatever.

I must say, right now I have a huge smile on my face that would make the Joker pale in comparison, as I now have a very solid 14v right from the start, even though the battery only had 11.97v. I haven't taken it for a drive, only started the car for a quick check so i'm not shouting victory yet, but... but .

I give it until friday before celebrating, and I think i'll reconnect the IBS as well.

 

Pleased you took the plunge and fitted it and found it straight forward. Fingers crossed you have sorted it out.
Cheers
Jim

 

Hi - your symptoms of wildly fluctuating voltage have been correctly diagnosed by previous responses in terms of the logical reason. This is 90% certain to be due to alternator/regulator problems. I have been trying to sort an E38 charging problem for weeks and have become far more informed by following this every step of the way.

The danger is that you are doing harm to your new battery by having the charging voltage so erratic. Certainly when you get above 14.5v you are beginning to cook the battery.

The questions I have are:

How old is the alternator ?
How old is the regulator ?
neither of these components are 100% reliable after 150k miles , although they can continue to work, they reach a danger zone in terms of failing.

When you first go to your car in the morning what is that voltage across the battery terminals ? This should be 12.7 ish - with a new battery it should not be below 12v. Monitoring that voltage after an overnight rest will indicate whether a parasitic drain is occurring, which is another area to examine if the alternator/ regulator route is not successful.

My advice - change the regulator immediately - the cost is minimal and it is a good investment anyway. If faults persist, the alternator is the next main suspect - I would not think that this would break the bank if you track down a proper Bosch remanned fully warrantied exchange. I have just bought a water cooled Bosch reman and the price was les than a quarter of the BMW price for a replacement.

The simple answer to correct voltage readings - when you go to the car expect circa 12.5vs ( use a multimeter not the OBC ). When the car is on tick-over with not a lot draining, the voltage will be circa 14.2v. With all accessories pulling hard ( lights, heater, A/c, rear screen heater etc ) the voltage will be circa 13.7v.

Measure voltage at the alternator and then check at the battery - what is coming from the alternator may not be reaching the battery ( that will usually be due to dirty terminals or ground connections - that means battery to chassis or engine to chassis .)

Finally, does the battery warning light illuminate when the voltage drops to 11 ish volts ? The warning light is designed to go off when the feed side ( coming from the alternator ) exceeds the static battery side ( coming from the battery ) - thus if your battery voltage is where it should be - 12.7 - the alternator must send at least 12.8+++ to extinguish the battery warning light.

I am trying to make this reasonably easy to comprehend as your problem is very likely to be straightforward rather than a convoluted mixture of electronic related possibilities.

Good luck - keep us posted as to how you progress.

 

Hi contimaz, as said just before your post I did replace the regulator.

I think it's all good now, after a week of driving, absolutely not a single issue, IBS has been reconnected as well.

Now i'm highly tempted to put back my 100Ah Varta in, as I think it just needed to be recharged and could still be going strong. Also it has the + and - in the correct sides (current one has them "reversed", which prevents me from putting the cover on it in the trunk).

old reg (brushes way too short)

New reg (genuine Valeo part), brushes are long enough

the rod they're supposed to be in contact with

 

Hey buddy. I’ve found this post really helpful and I am glad I came across it. I just have one question regarding the changing of the regulator. Did you manage to do it without getting the alternator out. If so how hard was it?

 

On some car's you can some you can't.
If you can get the tools in there .

 

In my case it’s a e60 530d from 2004. I think that the pictures provided from erherealedge97 were from the same model

 

There you go nice one.