[Dirtleg]

Hey new guy here. Been out of the BMW world for well over a decade but am now back somehow.

Anyway to the point. I have this e90 which is in need of some repairs. Been getting many weird codes and definintely a number of them are related to low voltage. Figure I need to solve this issue before going any further.

I am getting a consistent 2E97 (Returns after clearing) generator code. Also the battery icon shows on the dash.

Using Bimmerlink I've been able to determine the voltage drops at the battery as the car is running. Battery seemingly holds a charge when left overnight after charging. I unhooked the charger last night and this morning had 12.68 volts. I realize I do need to take it in for testing just to be sure it's not bad.

While the car is running the generator voltage output is 14.2. I can watch the battery voltage drop slowly at the same time. Oddly if I check the voltage with a MM at the alternator itself I get the same reading as the battery voltage and not 14.2V. Makes me wonder where the 14.2 reading in Bimmerlink is coming from.

I tested the alternator diode and it is good.

And yes the battery has been registered to the car.

Now in my experience all these signs would point to a bad alternator. But I am aware that these cars can be more involved in diagnosing the actual problem than most. On my older BMW's when I lost an alternator I would swap out the VR and be good to go. I see that is still an option on these cars but it seems it's only ever related to high voltage and not low. Wondering if swapping out the VR would be a waste on this car for that reason.

So in conclusion I believe I need a new alternator. If you disagree please let me know what other steps I need to do to confirm what the issue is. Thanks.

[Dirtleg]

Bump and an update. (This must be a taboo subject. No comments at all)

Battery has maintained it's charge connected to the car and outside in cold weather for 3 days. Seems like it's good. I am moving forward with the alternator.

Going to be doing CCV system, valve cover gasket, oil canister gasket, spark plugs etc next week so might as well get it all at once.

[gbalthrop]

Originally Posted by Dirtleg

... I am getting a consistent 2E97 (Returns after clearing) generator code. Also the battery icon shows on the dash. Using Bimmerlink I've been able to determine the voltage drops at the battery as the car is running. Battery seemingly holds a charge when left overnight after charging. I unhooked the charger last night and this morning had 12.68 volts. While the car is running the generator voltage output is 14.2. I can watch the battery voltage drop slowly at the same time. Oddly if I check the voltage with a MM at the alternator itself I get the same reading as the battery voltage and not 14.2V. [??]...

Welcome to the Forum!
Sorry I missed your original post. I'm NOT sure your "Charging" issue is due to Alternator output, or lack of it. ONE thing that can cause your issue, as I understand your description, is failing "Transfer Point" where the B+ Cable from the Battery (+) Terminal passes through the chassis ahead of & at base of the battery.

You suggest your alternator "Output" is 14.2V with engine running.
(1) HOW & (2) WHERE is that measured? I would suggest simply using a Multimeter to measure voltage, Engine RUNNING, (A) at the Jumpstart Terminals under the hood, then (B) at the battery POSTS in the boot. If the Voltage at the Jumpstart Terminals is significantly GREATER than at the Battery Posts, then you have a wiring issue, likely Transfer Point.

If you have MORE voltage at the Alternator LARGE Red Cable than at the Jumpstart Terminal, there is a wiring issue between Jumpstart Terminal and Alternator. If there is less than ~13.5V at the Alternator OUTPUT Cable end (at the Alternator), then you have an Alternator issue, OR Ground Cable issue.

Does the Starter always crank at 180-200 RPM as it should and engine start in less than 2 seconds of cranking? If so, Engine Ground Strap at Starter is likely OK, but there are tests for that if any question.

Your fault code appears to be related to Generator Temperature, and NOT specifically related to voltage output, per this Bentley Definition:
POA3B | 2E97 | Generator Over Temperature

Since I don't know anything about BimmerLink, I would rely on Multimeter Voltage readings, but please provide as detailed description as you can WHERE you are making those readings. Please also provide the Last-7 Characters of your VIN so we can provide specific ISTA wiring diagrams for YOUR vehicle.

For link to E9x References, including where to get INPA, Bentley, etc., see the pdf attached to this link:
https://www.bimmerfest.com/threads/e...ision.1426774/
George

[Dirtleg]

Thanks George for the clear and detailed response.

To answer your question about voltage at the Alternator large red cable that is where I got a reading of 11.98 volts at the same time Bimmerlink was showing 14.2. My reading at the battery terminals and at the underhood jumpstart terminals matches that of the alternator output. All 3 readings done with the same multimeter. And monitoring voltage from the IBS in Bimmerlink showed the same readings as the MM did.

My guess is Bimmerlink is reading from the voltage regulator connection and not the output voltage of the alternator. The reading in Bimmerlink did go up and down with rpm's and I saw it as high as 15v but battery voltage never climbed, just continuously drops slowly as the car is running. The generator power reading stayed at or near "0" the whole time.

And thanks for the links. I did find the Bentley yesterday in pdf format from a different site as sadly the Belton site link is down. It was obviously scanned so not perfect but good enough. The Training Manuals archive was excellent to. Much appreciated.

I have installed the Standard Tools from Bimmergeeks but have not yet purchased a cable. The other issue is mega is wanting a subscription to download either the DATEN files or ISTA+ as it says the transfer exceeds the available download quota for my ip address. Went through all that yesterday. Maybe I'll try through a VPN and see if that works.

Last 7 of VIN PT20332

[pedro2u]

great PDF summary of references in that link. Thanks George!

[Dirtleg]

Well I have more info now.

Extreme curoisity has had me going over all the documentation and searches I could find relating to the car charging system.

Alas my brain is so full I am forgetting things already.

But before it was lost in the gray matter I managed to remember to try checking the voltage at the jump start terminals with the car running and the BSD wire connected and disconnected.

There was no difference in output voltage. Battery was at 11.8 before starting car and 11.4 while car running. Reason battery was so low is because I haven't charged it in 9 days and I've moved car around a few times checking other things. Lights have been on, doors opened and closed repatedly etc. Never had a problem starting thankfully. It's on a charger, through the JST, now. Want a full battery when the alternator is swapped out.

My reman Bosch AL9358X showed up today again (1st was damaged in shipping) and is not broken thankfully.

My son, who just turned 16, wants to help work on the car so we will be waiting till the weekend to do any more work on it.

Will update with results when finished.

[Dirtleg]

Well it's time for an update.

Finished all the work we had planned on over the weekend. Just didn't finish till this evening. There were a fair number of other issues along the way. Look in the "what did you do to your car today" thread for that stuff.

New alternator installed. 14.29 volts reading at the IBS. Generator power reading fluctuates with electrical usage.

Old alternator was I believe oil fouled. Leaking OFHG did a number on it. There was so much oil caked inside, it was not smooth to turn it by hand. Not bad bearings, just caked oil being contacted by the armature. I did a degrease flush on it and it smoothed right up after that.

This car was definitely still running the original alternator. I may keep it and see if I can bring it back to life. Worth the $50 core charge IMO.

So yeah good news on that front.