[HugoCountsto7]

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[HugoCountsto7]

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[PhaseP]

The cable itself won't cause any problem with heat at all, it is a thick copper cable.
The connections at each end of the cable if corroded or loosened can cause problem. You can wiggle it and see if it causes the problem.
I still think you will end replacing your alternator, the new one.

[HugoCountsto7]

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[HugoCountsto7]

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[YouAreMyWorld]

I've unfortunately been dealing with a similar problem myself. I feel your pain greatly with how absolutely fucking frustrating (excuse my language) coupled with how intermittent this problem is. Except my issue is both an undervolt and overvolting situation--under hard acceleration the car will undervolt and the entire BSD line goes down. Meaning that the oil sensor goes offline. If you go WOT to near/redline, it will overvolt resulting in the trifecta of Christmas Tree dashboard, ABS, wipers, etc. depending on its mood (sometimes it overvolts under WOT and other times it does not).

All of this occurs about 45 minutes to an hour into driving. Whether in hot or 'colder' weather (as in day or late at night when it's much cooler)

Things replaced: Alternator, IBS, BSD cable, Oil sensor, Battery, Water Pump, AC Compressor, Junction/Fuse Box--all with genuine, brand new, OEM BMW parts. The only thing left to logically replace would be the DME. All connections have been checked/rechecked and all work has been done by a BMW/Mercedes (specialized) certified Indy shop.

I'm so discouraged with this fucking car right now, I honestly feel like getting rid of it, as this has been such a ridiculous experience that it's almost unfathomable. I wouldn't wish this on my worst enemy.

[HugoCountsto7]

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[PhaseP]

Originally Posted by DLoBrown

Any time I am in the car I have my customized Deep OBD app running with an alert tab. If the voltage goes over 14.5 volts I have it programmed to make a chime sound. I get a lot of 14.52 to 14.8 volt spikes during the week during: start-up of the car, when making sharp turns, and sometimes when coming to a stop. The start-up and coming to a stop spikes could be directly related to RPMs (which could be tied to the alternator by the serpentine belt), while the sharp turning spike are still a mystery. I have assumed that something is happening with the powersteering during the sharp turning spikes, and that affects the main serpentine pulley since the powersteering has its own belt directly to the main serpentine pulley. I don't know what's going on there, but I think they are related. A few times I got the big 16-17 volt spikes to appear while stationary, by pulling the steering wheel hard left or right.

You may be on the right track with the pulley or accessory belt.
It is possible something to do with the belt momentarily sliding over the crankshaft pulley. The alternator should have an "overrunning" pulley. The alternator axle clutches to the pulley turns with the belt at the correct rotation direction. But if alternator pulley slows down or even stops compared to the alternator axle, the alternator axle rotates freely. One possibility comes to may mind if the accessory belt is loose and slides over the crankshaft pulley if it is too loaded momentarily, alternator than will turn free. Although alternator should slow down fast due to electrical load on it instead of freely spinning fast.
But in any case if the belt slides and grabs intermittently under load from say the power steering pump, it may cause havoc on the alternator. And this may also tie in with the after engine warms up, the belt will also be warmed up. Just a theory.

Maybe check the belt and all the pulleys and the tensioner if you haven't done so? The tensioner and idler pulley started making light noise at around 60K miles on mine. Its bearings were getting toast. If your are not replaced yet, I don't they will be in good shape.

I think you had already checked the alternator pulley, if not check that too. If you block the alternator axle, like placing a screw driver inside but not to some place there are wires, winding, pulley should turn smoothly without resistance (only slight resistance) one way, but lock up with axle and not rotate if axle is blocked on other way.

The BMW guys around here just want to replace the DME. I wish I could get them to agree that if that doesn't fix the problem, then they have to give me all my money back. Since they won't do that, I won't risk it.

Since you have disconnected the BSD line to alternator and stil seeing voltage drops it cannot be related to the DMW.

Seeing occasional 14.8V is normal as far as I know.

Good luck!

[PhaseP]

Another thing is why drop to 8 Volts?
You have the battery connected. Even if alternator cuts, voltage should drop to battery voltage, which should be 12, 11 Volts depending on battery charge and electrical load. Worse should be 10 volts.

Dropping down to 8 volts is strange, it is indicative of something is shorting, like battery (or alternator) plus to the chassis.
Wonder if battery is disconnecting and connecting back intermittently, indicating something on the battery side connections or front distribution box where battery plus cable comes.
2007 or some year had recall on the front distribution box under the glove box for loose battery plus connection, if I remember correctly.

[PhaseP]

Another thing to check that comes to my mind is the DME relay.
It is this part for 2005-2007:

http://www.realoem.com/bmw/enUS/show...diagId=61_3933

It is inside the box where DME also is placed, that is on the other side from the brake fluid reservoir under the air filter housing. Sits on a "blade" inside there along with other fuses and relays.

And it could be DME itself too, since it is measuring the voltage and reporting.

[401FlaGATOR]

If all the grounds and positive connections are well connected to the battery then the voltage is incapable of dropping below the battery voltage (assuming well charged battery) unless there are huge current spikes which are causing the voltage to droop.


Of course there may be some intermediate high side driver (MOSFET) that may be between the actual battery and the car's 12V+ power bus. Excuse my ignorance about the knowledge specific to the car it may be the IBS is the high side driver? I'm just approaching this from my general backround as an embedded systems engineer.

I saw a graph a few pages back but did not or could not see the time durations of the spikes/ brownouts.

One would need to test to identify that these current spikes are indeed happening by monitoring current at the source (between battery positive lead to car electrical system).

If the current spikes are real one could then track down which circuit branch the spikes travel through which would lead you to the offender.

Measuring steady state currents are pretty easy to do using a cheap clamp ammeter. Fast transients might need a more sophisticated method involving oscilloscopes and measuring voltage drop across a known resistance in the milliohm range. If you had an oscilloscope probably wouldn't need a precise resistance as we could just measure tiny voltage drops along two points along the positive battery cable (2 points as far apart as possible on the same electrical node), and compare the normal behavior to the fault condition. You would set up oscilloscope so that very small changes in voltage drop along the wire can be detected. Ohms law, I =V/R. R is a constant in this test so changes in V on the oscilloscope would correlate to a change in I (current).

http://www.fluke.com/fluke/sgen/comm...amps/clampabcs

[401FlaGATOR]

Conversely if there are no current spikes, then there is not a short circuit condition occurring there is an open circuit condition occurring. Assuming you have all the proper grounding straps the open circuit condition would have to be occurring on the +12V bus. It would have to be something between the battery and the rest of the +12V bus. You could set up a voltmeter across these two electrical nodes (+12V of battery, +12V power rail of car) and when the fault condition occurs you would see a voltage of 4 Volts (battery voltage - 8 Volts ), where normally you should be reading 0 volts. This would be indicating that there is no initial current spike but rather an open circuit condition initial condition that decouples the battery from alternator.

I would bet this is what is occurring rather than the current spikes which would generate tremendous heat (unless they were extremely short duration).

[HugoCountsto7]

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[Vatrica]

Hello guys,

Plus one on the issue. Youaremyworld described my feelings perfectly.

Once in a month or two months, I get jumps from 8v to 18V, sometimes it gets over 20v and the car stalls following with no start situation for a couple of seconds. When I say no start, I mean dead like if battery was disconnected.

Up to this point changed alt and regulator, ibs is unplugged (noticed overall lower running voltage when unplugged). All grounding points checked and in good condition. JBE also changed, checked DME for signs of water damage, dry as dust.

Right now I'm planning on checking the above described pulley situation on old an new alt, I'll also look for a MPM module which allegedly only e60 has, but I think mine could also have one since its loaded with options...

Like he said, wouldn't wish it to the worse enemy. I don't have the guts to even sell it in this condition.

Many thanks from Croatia