If you are getting into 12v while running, you have a problem. Start at the alternator and see if you have a separate voltage regulator.

First indication is voltage regulator or slip rings. Is your alternator oily? Second indication is a bad ground. Check the ground by measuring the voltage drop from frame to block it should never be more than. 0.3v. (except maybe during start).

DME sockets checked, no visible issue, alternator also no visible issues

I will be replacing the battery today and am hoping this will solve it, although its never that easy with this car.

Will post results when ready

BR

Hi,

Voltage drop from frame to block is around 0.5v, or so the repair guy shop said.

All ground cables around it were rechecked and tightened, issue with the voltage drop is still there :dunno:

Should I go on with an alternator repair - i.e. voltage reg replacement?
I found a repair kit on ebay, Part Brand: LActrical, does anyone have any experience with them - are they reliable?

I can't find the bosch one anywhere.

Can it really be the voltage regulator that causes all this, or am I at a dead end

Any advise is again much appreciated. Truck is for the third week in the shop now,I'm getting desperate that they wont be able to find the problem :(:(:(

BR

BMW X5 E53 4.4 EU version help needed with Engine failsafe (Motornotprogramm)
 

1/2v drop on the ground strap seems excessive other than at start but if the voltage ever drops below 13 that's a sure sign of VR failure.

Confirm by measuring the voltage from B+ terminal to the engine block. If you get similar drops in voltage than the alternator is the fault.

When mine died it was the slip ring/ brushes and I replaced them with a &20 kit. Other than bearings those are the only parts that really ever wear. The stator windings are locked in enamel and can easily last a million miles.

Measure the ground strap voltage at start and confirm the 0.5v was just normal running. I found my problem before I got that far didn't need to test my ground strap so don't have a baseline. Within the past year somebody on xo had a loser ground strap causing his similar problems

Hi all,

long story short, after replacing the battery with a new one and retightening all grounds around the block car runs fine. Reseted adaptations as well, first time not the right way (car was running), second time the right way with the gas pedal all the way down for 31 seconds and key at pos 2.

1000km now and no issues with the rpm. Read the voltage with inpa, they still drop below 13, but only briefly.

Thanks all for the help. No I have to fight only the servotronic, after the summer tire change (from 18 to 19) my steering is crap, parking is a pita without it. Its a never ending story with this car.

BR
Dimitar

Sorry, but pressing the gas pedal doesn't reset anything - that's an urban myth....

And if you see your alternator voltage drop below 13v at any time, your alternator is possibly on the way out. The new battery won't last long... :(

Like you said - it never ends. :confused:

I don't know really. Before the gas pedal reset the car didnt even wanna start. After that it fired up right away. Dunno what we did, all seems fine, for the past 10 days. The old battery went in another car after sitting for 10 days in my boot. Fired up without any issues, was an audi a6 3.0 diesel, which leads me to believe the old battery was also fine

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