Alternator or Voltage Regulator?

[Kern47]

Hoping some of you electrical whizz's can lend some advice here.

My M died last night and the alternator was the fault. Got it back home and got the alternator off.

From those pictures, does it look as though the voltage regulator has worn out? The bearings are all good and theres no obvious signs from the alternator that theres an issue with that.

https://m.buycarparts.co.uk/hitachi/8947527

Hoping I can buy that part listed above to solve the issue and save me some money this close to Christmas. Hopefully getting it on the road so I can travel home next week. The other option being buying a cheaper aftermarket replacement and hoping to God it's going to fit (seem to be a whole load available for the M and all slightly different).

Not sure what else causes alternator failure, or how to diagnose it?

Any help will be much appreciated.

 

[Smartbear]

Did you carry out any electrical tests on the cars charging system before you dismantled the alternator? What voltage did you have at the battery with the engine at idle/revving?
Rob

 

[Kern47]

Did you carry out any electrical tests on the cars charging system before you dismantled the alternator? What voltage did you have at the battery with the engine at idle/revving?
Rob

I had the RAC out to recover me, he checked the voltage and basically came to the conclusion that the alternator was dead and not charging. Other that that, no I havent. I dont have a multimeter and am pretty clueless when it comes to wiggly-amps anyway so I decided to just take it off so it's ready for the replacement.

What else is there to go wrong with an alternator though? Its spinning and theres doesnt look to be much else to it other than that regulator?

 

[AndyBeech]

Where are you based, got an old but working alternator somewhere (I think) if you want it.

 

[Kern47]

Where are you based, got an old but working alternator somewhere (I think) if you want it.

I'm in Lincolnshire, very rarely anywhere near anyone in these situations

 

[Kern47]

Just an update if anyone else runs into the same issue. I swapped the alternator for the one posted above, and the problem appears to be fixed. Given the car a run and everything worked fine.

Although even after an hours drive... I was woken in the middle of the night to my alarm sounding with no way of turning it off, so the battery is clearly dead. Awaiting a new one and then fingers crossed, issue solved

 

[Ewazix]

Your slip rings (the copper sleeves) and brushes were completely worn out, typical repair kits with bearings are about £10 on ebay. The rings & brushes are not too difficult to replace but bearings can be hard work depending on the unit as they need drifting in/out.

 

[ph001]

If the alternator is not producing any output but is spinning OK then it's nearly always because the field wingdings are not being energised (in which case you get the red light on the dash) or the diode pack on the stator is dead. The field winding is what is powered through the brushes and slip rings in the picture. When the field windings are powered, this sets up the moving magnetic field (because the alternator rotor is spinning) which results in the main windings on the stator generating power which goes out on the main B+ terminal.

The regulators job is to increase or decrease the current in the rotor field winding (which increases or decreases the magnetic field) which in turn changes the alternator output voltage. When the regulator semiconductors die, the usually go short so you typically get too much voltage on the battery (especially when you rev the car). If the brushes and slip rings wear out you typically get to little volts on the battery.

 

[Kern47]

Your slip rings (the copper sleeves) and brushes were completely worn out, typical repair kits with bearings are about £10 on ebay. The rings & brushes are not too difficult to replace but bearings can be hard work depending on the unit as they need drifting in/out.

slip.jpg

Having not seen that post before... It would now appear that you're right. The new life in the brushes lasted a while, but I'm now getting the same issues returning (presumably due to the worn slip rings). Do you have a part number/link to the correct slip ring replacement part? Hopefully I can get it fixed this week (after a long, hopefully uneventful, trip down to my parents). Thanks

 

[Ewazix]

Your slip rings (the copper sleeves) and brushes were completely worn out, typical repair kits with bearings are about £10 on ebay. The rings & brushes are not too difficult to replace but bearings can be hard work depending on the unit as they need drifting in/out.

slip.jpg

Having not seen that post before... It would now appear that you're right. The new life in the brushes lasted a while, but I'm now getting the same issues returning (presumably due to the worn slip rings). Do you have a part number/link to the correct slip ring replacement part? Hopefully I can get it fixed this week (after a long, hopefully uneventful, trip down to my parents). Thanks

You will have to check it against your particular year/model, either google or Real OEM should find it OK
https://www.realoem.com/bmw/enUS/select?product=P&archive=0&series=F85

 

[Kern47]

[/quote]

You will have to check it against your particular year/model, either google or Real OEM should find it OK
https://www.realoem.com/bmw/enUS/select?product=P&archive=0&series=F85
[/quote]

Thanks, forgot about Real OEM :roll:

For future reference for anyone else with the same issue...

The part number for the OEM alternator is 12317837691

A quick Google of "12317837691 slip rings" throws up a link to Online Car Parts (looks to be another version of the German sites, autodoc, buycarparts etc.). Where their article number for the slip ring is CQ1070001.

That shows a couple of options, the most 'expensive' being this one for £5.50. Does this look to be the correct one at 52.1mm? Also, is there anything else that I'd need/would really benefit from being changed? It's already got a new voltage regulator with the brushes, and the bearings aren't giving me any issues atm so dont really want to go through the process of changing those. Thanks

 

[Ewazix]

You will have to check it against your particular year/model, either google or Real OEM should find it OK
https://www.realoem.com/bmw/enUS/select?product=P&archive=0&series=F85
[/quote]

Thanks, forgot about Real OEM :roll:

For future reference for anyone else with the same issue...

The part number for the OEM alternator is 12317837691

A quick Google of "12317837691 slip rings" throws up a link to Online Car Parts (looks to be another version of the German sites, autodoc, buycarparts etc.). Where their article number for the slip ring is CQ1070001.

That shows a couple of options, the most 'expensive' being this one for £5.50. Does this look to be the correct one at 52.1mm? Also, is there anything else that I'd need/would really benefit from being changed? It's already got a new voltage regulator with the brushes, and the bearings aren't giving me any issues atm so dont really want to go through the process of changing those. Thanks
[/quote]

Double check that you have a Bosch alternator and not an alternative, if it's Bosch it should be OK. Alternative (complete alternators) are interchangeable, but internal components might not be.