2008 X5 3.0si - electrically

[andrewwynn]

Do you have n52 motor? I replaced starter on one this year it's not difficult just lots of steps. Took me about 5-6 hours over two days but I did do on a Chicago street.

If you have a digital multi meter you could use the same trick to test starter current. Measure voltage drop from cig lighter to B+ and somebody else can measure the same to get a control.

Learn to use the hidden menu and watch the bat voltage while driving. If the voltage drops below about 12.5 the alternator is the problem.

I think it's easier to get to than on m54 if memory serves I may have had to remove to do the starter. It felt like I removed 1/3 of the engine.

[LennyBoy1]

I reviewed the Foxwell NT510 and watched a few video reviews by some BMW owners. It’s about $240 in Canada on Amazon.ca but I think it’s probably the best and worth it considering it will do just about anything a BMW dealership can do. According to my research some BMW owners have recommend BMW Scanner 1.4 (OBD Connector with cable to connect to laptop). There is another scanner on Amazon called ANCEL BM700 All System for BMW & Mini vehicles with very good reviews.

[LennyBoy1]

Hi, yes I have the N52 3.0 litre inline six....which I intentionally purchased. It’s a great engine but apparently has a terrible starter location! I am just researching which advanced OBD scan tool I should purchase and so far the Foxwell NT510 appears to be the best based on its functions and price.

Please let me know what scanner works best for you. Thanks

[LennyBoy1]

Thanks - I’ll try to find the hidden menu for the battery voltage and go for a drive later this week.

[andrewwynn]

510 is what I have. 520 functionality the same but without a reset button. 530 should also be equivalent but make sure your anti virus is up to date, rumor was the install package was infected.

[pshovest]

Originally Posted by andrewwynn

..........they said it should stay down regardless of RPM. If the voltage swings from RPM the VR is not doing its job.....

Not sure who "they" is, but this is wrong. The alternators out depends on two things, excitation current provided by the regulator to the field coil and alternator speed. This is why system voltage rises with engine speed. Most alternators cannot produce full 180/220 amp output at idle speed.

[CLS70]

a few years ago I bought USB adaptors that come with an embedded Voltage Meter; they are inexpensive and provide a quick checkpoint; they may not be accurate but you can see if something has *changed*.

When I get into the car, in the ON position (without the engine running), I normally get around 12.0 - 12.2 V (see pictures), when running, I get 14.5-14.9v.

If I'm parked, engine off, using the radio, using the vent/fan, after 10-15min, the voltage drops to 11.4 and stays there until the car goes to sleep.

[LennyBoy1]

I already own a OBDLINK MX Bluetooth scanning device....can someone recommend a BMW scan software that might work with this for registering a battery?

I recently used this device along with a scanning software purchase to activate an oem factory brake controller which I had installed.

[andrewwynn]

Originally Posted by pshovest

Not sure who "they" is, but this is wrong. The alternators out depends on two things, excitation current provided by the regulator to the field coil and alternator speed. This is why system voltage rises with engine speed. Most alternators cannot produce full 180/220 amp output at idle speed.

The VR changes the excitation current nearly instantly to keep the output voltage nearly the same at any RPM.

Though there may be some limitation to the max current at low RPM that will work itself out with laws of physics.

The Alternator is 3 phase and will generate high frequency AC maybe 1.5-3x the RPM and that is rectified to bumpy DC.

There is no reason alternator can't be designed to output any voltage any RPM any current so I'd have to see the output design limits to see if the can't output full current at idle. It just would mean it would take a lot of torque and the armature current would be a lot.

That is the failure mode of both of my X5 alternator: the brushes when they get worn can't supply enough current to maintain voltage at idle and that's the best initial symptom that the brushes are worn.

In normal circumstances the output voltage should not drop lower than about 0.4v any RPM though there certainly can be design limits eg might lose a volt at max current at idle. 2000w or so at max power is as much as a starter.


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