M30 running on 3 Cylinders !!! help

[Javier]

then you have to have turned on a red light with a battery icon. As you may see from the charging circuit drawing, the unloader relay has a diode that feeds the alternator rotor for start up (wile the residual magnetism isn't enough to generate something). If this diode is opened (damaged), then you will nave the described symptoms, and the battery light will not go on.

Yes I would check the unloader relay, as it may be the key to your alternator issues.

See this threads for help:

http://www.bimmer.info/forum/showthread.php?t=10435

http://www.bimmer.info/forum/showthread.php?t=8970

Javier

[pink-planet]

I still don't get it, it's something with certain input and certain output, and the people who developed the car should have thought of all the possibilities, which may cause problems and how to fix them, didn't they?! Anyway, wish you solve your problem with your car as soon as possible.

[grave77]

thanks mate, it's starting to reveal the reason one test i have to report back to Javier and i think i would know whats wrong.

[Rustam]

thanks mate, it's starting to reveal the reason one test i have to report back to Javier and i think i would know whats wrong.

GRAVE I have mentioned location of unloader relay in my post back to you (and spent good time typing too) - that relay is located in electronic box on the left side of the engine compartment, right before the windshield...
generically, UNLOADER RELAY is third one from left in the row next to FUSE FILE...

AND I agree with Javier - based on what you said - the only relay that participates in transfer of electricity with the alternator is unloader relay

Now JAVIER - regarding the diode - Bentley's manual for e34 says that the diode is only used in M5. Can you comment on this?

[grave77]

thanks mate, but I don't remeber you mentioning the unloader relay, you were totaly against it. still I'm going to do that today. I hope this is where my problem is ... my car is in the parking since last week ... I'm driving a Honda Civic now ... I can't wait to drive my bimmer again ... crossing fingers.

[grave77]

those 2 threads r gr8 !! .. I'm hoping it's not a cable problem as when they replaced my transmission to manual they were messy so I hope no wires been disconnected. I'll check it today when am back home.

thanks Javier ...

[Javier]

but unloader relay is shown in the drawings with a diode inside the relay.

See picture

http://www.bimmer.info/forum/attachm...1&d=1105812969

Javier

[grave77]

ok ... I extracted the unloader relay and tested the diode with an AVO meter ... test was OK, terminals r clean. so I need to test the other diode, that's if it exists in my car.

I also went down and grounded pin number 4 and the light glowed.

when I tested the field connector on the alternator, the power is not getting there until I throttle the engine.

I checked both fuses 17, 28 they r ok, I think the uncoupling diode is open.

some strange signal was on the diagnostic connector Pin 13 .. its signal was rough and the engine was rough just the same as it was on this pin.

this is all what I found. ...

[Javier]

Let's test continuity from pin 9 of relay socket (corresponding to pin 85 in relay) to pin ** 12 ** on diagnostic connector, should have ~0 ohm reading.

If OK, also test continuity from said pin 12 and the terminal D+ at the alternator (the small live connection), also should get about 0 ohm reading.

With the ** engine off **, and key in run position, if you ground pin 12 at diagnostic connector (or terminal D+ at the alternator), battery warning light should go on. This will also verify continuity.

Edit: May be your mechanic unpluged X6508 and never put it back!! See picture.

Javier

[grave77]

Thanks mate, I will check this for sure, I have unpluged this cable when I removed the head, maybe the wires were dry and caused some disconnection. I will inform you soon