[accventures]

My daughter's 2014 X3 has become a $5,000 money pit in the last three months. It has about 120,000 miles on it. We have replaced a leaky valve cover, battery, plugs, belts, leaking oil somewhere else and can't recall what that was except expensive.

About a week ago, the car alarm started going off in the middle of the night. Door locks would not work, couldn't;t get the alarm to turn off with the FOB. Check engine light on. Eventually got things to turn off, took it to a mechanic and told it was a bad battery. We replaced the battery, everything worked fine, car started right up, all check engine type lights went off. My daughters driven for about a week now with zero issues.

Went to drive the car today and FOB would not work. Eventually got into the car and tried to jump it which didn't;t work. Door locks won't work, no lights, no sound, no anything. Dead. She went to get a new FOB battery and that did nothing.

So I assume it could be a bad alternator base don research I've done. Maybe could be a bad FOB but I've never seen one go bad in any of the BMW X3's, X'5, X1's we've owned. So I go back to alternator since it is DEAD DEAD and literally not a single thing in the car works. Also see that a bad voltage regulator could be the cause but more likely the alternator. Before we have AAA get it to a mechanic Monday, wanted to see what the forum's thoughts were.

Thanks in advance!

[Ivan67]

Have you checked for a parasitic draw?
I had a similar issue with an E46 M3, and it was the blower motor resistor that kept draining the battery. Not sure if the F25 is constant powered system.
Good luck.

[Opie55]

You're probably a one-time poster who won't come back to let us know what it was, but for future reference you left out what the condition of the battery was when it would not start the last time. If it was dead, that points to one thing, if it was still charged, that's a whole different set of things.

[frisbeeguy]

You didn’t just buy a BMW if money was of any concern, did you?

[pole1980]

Originally Posted by Opie55

You're probably a one-time poster who won't come back to let us know what it was, but for future reference you left out what the condition of the battery was when it would not start the last time. If it was dead, that points to one thing, if it was still charged, that's a whole different set of things.

I am also curious what it was, something like that happened to my wife's F48 X1, the car wouldn't unlock from the key, completely dead. We changed the car battery, after that, the car seemed fine for about one day, then died again, no power, nothing.

Tuned out it was the ECU, flooded with fuel. There is a certain sensor on the return fuel line, that cracks and the fuel travels via capillary action through the wiring loom, directly into the ECU.

The fuel lines were replaced (the sensor is part of them so it's not available as a separate part), the ECU was opened and cleaned and the problem was solved.

Apparently, it is a pretty common issue with this sensor crapping out, so I was told by the dealer, pretty shitty design tbh.