28D7 E53 4.4i N62

[AussieE53]

Morning all, I’ve had a charging issue I’ve been trying to resolve over the last 12 months.
Symptoms were poor or failure to start ( trans fault throws when voltage and charge gets low).
No Charge or Battery warning light.
I replaced the Battery
I replaced the Starter
I replaced the Alternator
Issues still exist
I’ve checked the Error Codes
28d7 Generator Communication error shows
When cleared it comes back
I then checked the Single wire that runs to the Alternator and it shows 8plus volts which I understand is correct.
I checked the Alternator output on the Alt Positive post when running and it shows 13/14 volts.
Running the test on the dash shows 11 / 12v
Bringing the revs to 2000 and switching the headlights on doesn’t show any real increase or decrease in voltage
What should I do next ? Help.

Edit-Should add I live in Central Queensland and our nearest dealer is over 2hrs away.

Where would i find a wiring diagram for the DME so I can trace the alternator signal line

[timmyc]

Sounds like a possible Final Stage Resistor (FSR). Your symptoms sound similar to what my daughter was experiencing in her e46.

We had basically an all new charging system and she was still having a voltage draw. We noticed it more in the cold weather and if she didn't drive for a few days.

Took it to our indy and he diagnosed the bad FSR and she hasn't had an issue since.

This is just a shot in the dark, but the older bimmers are known for having this issue.

Good luck!

[AussieE53]

Thanks Timmyc, Thinking I may have to cave in on this one and track down a specialist. Crazy to think that at FSR might relate to the issues that Im seeing concidering the 28D7 Generator Communication fault code.

I'll keep plugging away in the interim...

[timmyc]

Have you tried disconnecting the lead to the alternator after having a fully charged battery? Worth a shot to try and isolate the problem?