Alternator worries

[Mangozac]

It looks like I may be having some alternator woes, so I wanted to get a bit more info on the alternator and regulator used on the Z4M.

Twice in the past week, both on cold days (cold by Australian standards - less than 15°C!) the battery indicator on the dash has lit up just after starting the car. Both times the indicator automatically extinguished after driving a short distance. I connected ISTA today and the DME had logged the fault "2E97 Alternator". There wasn't any further pertinent information given.

Unfortunately it seems that the alternator used on the Z4M is different to that used on the S54 in the E46, which is a pain. Replacements look to be expensive. Theoretically the fault could be with the regulator module on the back of the alternator. At 100k kms the brushes should not yet be a concern. Does anybody know what regulator module suits this alternator? ECS lists this one for the Z4M but it has no BSD connector and looks nothing like the one on my alternator. This one looks much more similar but I can't find any information as to the compatibility.

My battery was replaced late last year and the car still seems to have no trouble charging it. Most failure modes should be detected by the regulator module and specifically reported over the BSD bus to the DME, rather than this "generic" fault being reported.

Can anybody shed some light on this?

 

[ph001]

Just after starting is when the alternator is put under the most load as it has to dump a lot of current back into the battery. Could it be something as simple as the serpentine belt slipping a little (although you can usually hear this)?? If you are on the original belt at 100k then it's probably due a change anyway. Otherwise it could be a high resistance / corroded power or earth connection resulting in the alternator volts dropping under high load... or of course it could be the regulator pack as you suggest.

 

[Mangozac]

Could it be something as simple as the serpentine belt slipping a little (although you can usually hear this)??

Your line of thought makes sense, but surely there would be a noticeable noise, even if just briefly? Last I checked the belts still all looked ok but it's certainly worth giving them another visual. The tensioner would also be fairly easy to check. So although worth double checking, I'm dubious that the belt could be the source of the issue in this case.

 

[ph001]

I would agree - it's just something easy to eliminate and that can only be a good thing. Can you get a couple of voltage test probes to measure the voltage directly out of the alternator? You need the red probe directly on the B+ and the black one on the alternator casing (the alternator is earthed through the engine block to chassis). Then look at the voltage when you are getting your batt indicator light showing. If it stays above 13.8V then your alternator is prob ok and it could be bad earth / power connection. If it drops below 13.8V it will most likely be regulator or brushes.

To test for the bad earth, look to see if any volt drop between the case of the alternator and chassis, it should be <100mV. Similarly measure volts between battery positive and the B+, this should be less than 500mV worst case.

Also, you can pull the BSD connector out of the regulator pack to eliminate a charge control problem. With this disconnected it just functions as a regular alternator and o/p voltage should be constant 13.8 - 14.4V

 

[Mangozac]

Both good suggestions so I will give them a try also.

My concern is that if I do diagnose it to be a fault with the regulator that the regulator is not listed as a separate part for the Z4M. Only the complete alternator/regulator assembly. I'm trying to see if I can find any info from Bosch as to the regulator used inside the Z4M unit..

Update:
I gave the belt a visual this morning and its condition still looks very good. The battery indicator light didn't come on this morning but I checked the alternator output after startup and it was a very healthy 14.6V. Voltage drop between the alternator body and the jump start earth contact was only 50mV.

 

[ph001]

the regulator is not listed as a separate part for the Z4

yeh, weird. Even real OEM doesn't show a part number for it. Can you actually see the regulator part number (maybe get a smart phone down there and take a pic)?? Can't understand why it wouldn't be replaceable...or indeed why it would be different to the E46 M3.

 

[Mangozac]

yeh, weird. Even real OEM doesn't show a part number for it. Can you actually see the regulator part number (maybe get a smart phone down there and take a pic)?? Can't understand why it wouldn't be replaceable...or indeed why it would be different to the E46 M3.

The Z4M unit is higher output: 150A vs the M3's 120A. Maybe due to the electric cooling fan on the Z4M (not that that accounts for 30A of difference)?
If it continues to play up I'll pull it off and see if I can grab a part number of the regulator module. I doubt any identifying numbers are visible without removing the back cover of the alternator.

 

[mmm-five]

I believe it’s more than just a normal regulator on the back, which includes some charging control module.

I never found a reliable source for the back section only, so ended up replacing my whole alternator with one from ECP for less than 1/2 what BMW wanted.

 

[Mangozac]

I never found a reliable source for the back section only, so ended up replacing my whole alternator with one from ECP for less than 1/2 what BMW wanted.

That's not what I want to hear
You wouldn't still have the part number info handy would you? I am aware that the regulator is a "smarter" unit - it has the BSD interface for communication with the DME. From photos I've seen it looks to be physically identical to the E46 one, except for the current rating.

 

[mmm-five]

That's not what I want to hear
You wouldn't still have the part number info handy would you? I am aware that the regulator is a "smarter" unit - it has the BSD interface for communication with the DME. From photos I've seen it looks to be physically identical to the E46 one, except for the current rating.

I haven't sorry. It was a few years ago now, and it was all sourced by my spanner monkey.

I know the total cost was about £220 (plus core return surcharge of £100 or so) from EuroCarParts (IIRC). Which is much better than the £600 BMW wanted.

I can't remember what make it was, and won't be able to check until Friday...but in the meantime, here's a site with some 'budget' options (never used this site before, but it came up on a google search).

 

[Mangozac]

Ahh sorry mate, I was referring to any part numbers on just the regulator module itself in the back of the alternator.

Thanks for the links, but being in Australia makes things difficult when there is a return core charge involved :/

 

[ph001]

I think you will have to bite the biscuit and remove the cover to get to the regulator part number - then everything gets easier. The regulator isn't directly related to alternator current output capability of course, it controls the current into the field windings - so the E46 M3 one might well be the same part.

 

[Mangozac]

I think you will have to bite the biscuit and remove the cover to get to the regulator part number - then everything gets easier.

Yes, I think so. Fortunately it's not too painful a job and when I do I'll most certainly share the results here!
You're right in that the regulator simply modulates the field windings, but it's still using a closed loop control which I presume is current and voltage based. Still it's worth checking - we might be lucky.

 

[dannytheduck1985]

Only scanned the thread

Cut a long story short.

Get the alternator refurbed (includes diode plate replacement) and replace the stupid module on the back (cost me £180 for the module)

 

[dannytheduck1985]

If you get stuck, whip the alternator off and ship it to me. I’ll get it sorted

 

[srhutch]

If you get stuck, whip the alternator off and ship it to me. I’ll get it sorted

From Australia?

 

[dannytheduck1985]

If you get stuck, whip the alternator off and ship it to me. I’ll get it sorted

From Australia?

Australia

Come on man your on my page. Anything is possible. Sending a part the other side of the world sounds costly but to get it back working.......... priceless :wink:

Could end up paying double the cost with hit and miss idiots (we know I’ve encountered them)

 

[Mangozac]

If you get stuck, whip the alternator off and ship it to me. I’ll get it sorted

From Australia?

Australia

Come on man your on my page. Anything is possible. Sending a part the other side of the world sounds costly but to get it back working.......... priceless :wink:

Could end up paying double the cost with hit and miss idiots (we know I’ve encountered them)

Hahaha thanks for the offer mate but at this stage it still seems to be 99.9% functional so I'm not quite ready to start physical diagnostics

I'll eventually pull the back off it and see if I can ID the regulator module...

 

[Mangozac]

Following up on this:

My battery light on the dash is coming on very frequently now, even when it's warm. The concerning thing is that when the indicator light turns off it seems to coincide with some kind of electrical event which causes the entertainment system to reboot. Not ideal!

So I pulled the alternator and prised the back cover off to see the regulator. It's nothing like either of the regulator modules alluded to in my first post and is actually a Valeo 2542604. These can be found for feasible prices.

While I had it off I checked over the rest of the alternator. The brushes are still fine. The slip rings are appropriately worn for 100k KMs of service bit still plenty of life left in them. The shaft has no movement axially or radially and spins very freely, however it does make a very slight ticking noise. Diodes all checked out OK.

So at this stage I'm still thinking it's an issue with the regulator module - that's all the DME is still reporting. Thus I need to decide whether to just replace the regulator module or get a whole new alternator. I'd really rather not the cost of the latter....

 

[ph001]

I'd just replace the regulator pack!