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  #1  
Old 01-18-2022, 06:59 PM
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03 X5-ECU Not Turning on Alternator-Zero Voltage at Connector

EDIT: PROBLEM SOLVED. The alternator was still bad even after the rebuild. The shop that did the rebuild missed a bad diode. Once I installed a properly working alternator, all is good again and most of my electrical issues went away.


New to me 2003 X5, 4.4. I knew there were electrical issues when I bought it and trying to sort them out. Just had the alternator rebuilt by a very reputable shop. I am NOT getting any voltage at the plug from the ecu to the alternator. So the alternator is not turning on. Can anyone confirm:

1. What voltage should I have at that connector when unplugged from the alternator. The rebuild shop told me I should have 12v at that connector. I have zero.

2. What fuse is related to the alternator. Nothing references alternator/generator on the fuse map.

3. Any tips on troubleshooting the turn-on wire for the alternator?

Edit: Car starts and runs fine, just drawing battery power.

Last edited by Explorerlyon; 01-25-2022 at 10:03 PM.
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Old 01-18-2022, 07:39 PM
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Looks like F5 (glovebox) is the fuse in question...

https://bmwteka.com/wds/en/e53/0867beec
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Old 01-18-2022, 08:33 PM
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Quote:
Originally Posted by wpoll View Post
Looks like F5 (glovebox) is the fuse in question...

https://bmwteka.com/wds/en/e53/0867beec
Thank you!!! Fuse 5 is good (darn). I also just went and tested every fuse in the box and all were good. The only bad one was for the cigarette lighter (F25).

Now that I know the fuse is good and which fuse it is, I guesss the next option is to trace the wire back from the alternator to wherever it goes and hope to find something amiss.

Last edited by Explorerlyon; 01-18-2022 at 10:28 PM.
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Old 01-18-2022, 08:37 PM
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I think the alternator excitation shares the wire with the oil level sensor but also goes through the dashboard.

Usually somebody a little smarte than me will show a picture of the wiring diagram.


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Old 01-18-2022, 08:55 PM
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Old 01-18-2022, 09:09 PM
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Do you have 2 wires (green and blue) in the small connector? And 2 matching connections in the alternator?
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Last edited by 80stech; 01-18-2022 at 09:12 PM. Reason: wording
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Old 01-18-2022, 10:13 PM
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Quote:
Originally Posted by 80stech View Post
Do you have 2 wires (green and blue) in the small connector? And 2 matching connections in the alternator?
Yes. Here is the connector with two matching connections in the alternator. I just realized from the wiring diagrams linked above I was testing these two wires at the connector wrong. I am recharging the battery and will then update the voltage measurements at the connector. I measured across the pins, not each pin individual to ground.

Name:  Connector Two Wire.jpg
Views: 798
Size:  130.5 KB


Not to muddy this thread, but in case it points to other items to look at, I also have this:

Name:  Compustar.jpg
Views: 743
Size:  204.2 KB

I have not found an antenna or control box yet for a compustar system. It only locks and unlocks the doors. The prior owner said the original remote stopped working so they got this compustar remote instead. I have yet to dig under the dash to see what exactly this system is. I have focused on getting the alternator working and proper power to the car.

Last edited by Explorerlyon; 01-18-2022 at 11:01 PM.
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Old 01-18-2022, 11:03 PM
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Are you testing the green or blue wire? Are you testing with the connector connected (back probing.) Green comes from fuse F-5 which has a fair bit of stuff on it. Blue goes to the DME but through an additional connector.
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Old 01-19-2022, 12:00 AM
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Quote:
Originally Posted by 80stech View Post
Are you testing the green or blue wire? Are you testing with the connector connected (back probing.) Green comes from fuse F-5 which has a fair bit of stuff on it. Blue goes to the DME but through an additional connector.
UPDATE: Redid my voltage testing.

Ignition on: Blue: 11.84v Green 12.10v
Engine Running: Blue: 11.9v Green 11.31v

I do not have a way to back probe the connector (but just ordered some new test leads to do so in the future).

I have to conclude that my newly rebuilt alternator is not good. I will pull it out (again) and go have it tested and rebuilt. My concern was the computer was not telling the alternator to turn on.

Battery voltage: 12.54.
Car running my voltage measured directly on the alternator terminal (+) and case(-) is also 12.54. No change to voltage when I rev the engine.

The rebuilt alternator tested good when I picked it up. I hope something in the car is not killing the alternator regulator.

I appreciate all the help
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Old 01-19-2022, 01:28 PM
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My 2nd last alternator lasted one drive. VR went out on the second drive. That was a Bosch. I had the same concern after I read that the oil level sensor can kill an alternator. I switched back to valeo. That one lasted until my car was killed by a deer.
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