Alarm keeps going off randomly

[aj4937]

Hi all, I have recently purchased an 03 plate 3.0l z4 and am having problems with the alarm going off at random times. It is quite frequent and there appears to be no cause. I have read it may be the bonnet sensor and have tried locking the car with the key to avoid turning the alarm on but it still does it. Any ideas what might be causing it? When the alarm does sound it's just the beeping, the lights don't flash and there are no visual signs that anything is happening. I've had to leave my car unlocked for now so I would like to fix it quickly.
Many thanks for your replies,
Aaron

[A320_phill]

If it's not the bonnet sensor, could it be that something in the car isn't closed properly I.e glovebox or other cubby holes, or window?

I had a nightmare with my old boxster alarm and it was because one of the interior storage compartment doors wasn't quite closed properly, and it was monitored by the alarm!

Of course I maybe wrong with the Z4 but worth a look.

[CR55EDS]

It's probably the bonnet sensor. An easy way to diagnose is to lift up the bonnet and clip out the sensor. Close the bonnet and see over the next few days if the alarm goes off or not, putting the alarm on as usual. If no alarms going off, then it's the sensor. I can't recall how much I pad for my sensor from stealers but £15-£20 comes to mind.

[A1GSS]

I had this on a 2007 Range Rover which is full of BMW ECUs and electronics, so there might be a connection - the bonnet sensor was te immediate suspect but replacement didn't help- turned out it was the tilt sensor.

[dazols]

it is normally the bonnet pin, have you tried unplugging the sensor and locking the car with the keyfob? even though you have looked it with the key the alarm may still be active. i had this with my z4 when i first got it. i changed the sensor and its been as good as gold.

[aj4937]

Thanks for the replies, however it's not the bonnet sensor as I unplugged it and it's still doing it. Its more predictable since this morning though, the alarm sounds about 30 seconds after locking each and every time. Any other suggestions? I don't want to have to take it to BMW and can't keep leaving it unlocked. Is there a way to disable the alarm? I've tried locking with the key yet it still seems to be setting the alarm.
Thanks

[aj4937]

I have also just tried pressing the lock button twice as advised elsewhere but the alarm still goes off. The noise is a high pitched beep beep beep if that signifies any particular problem.
Thanks

[Fast3000]

I had a similar issue, checked all of the above but it turned out that loose change / coins in the ashtray or small cubby along the arm rest can set the the alarm off. I think its to do with the microwave sensor. Basically I took the coins away and problem solved

[aj4937]

Right I decided to remove fuse number 30 which is for the thiefproofing system and central locking. It's not ideal but it seems to have stopped it for now. At least I can now lock my car. The funny thing about this is that I didn't even know it was my car at first. I could hear the siren but as I didn't see my lights flashing I assumed it was someone else's! Does anybody know how much bmw would charge to diagnose in the UK? Got a good feeling I won't be able to get to the bottom of it myself.

[wattsie]

If I remember correctly doesn't the light under the rear view mirror flash to say there is a problem with the locking, or the cars not locked properly? Might have this mixed up with my old car though?

[CR55EDS]

Pressing the lock button on the key fob twice turns off the interior sensor and is helpful if you have an animal along for the ride and want to lock said animal in car when you alarm it!!

[aj4937]

I've tried pressing the lock button twice but it still happens. Could it be related to a bad battery? The dealer had to jump the battery when I took it for a test drive, though the battery seems OK now - no trouble starting.

[CR55EDS]

Pressing the key fob twice will not turn off your external alarm, only the interior motion sensor. I had a quick read of the handbook and it appears you cannot lock you car without alarming it, either all(interior & exterior) or just externally.

[mac27040]

If you can get someone on here local to you to hook up DIS v57 it will tell you what the problem is, if it's the radar burglar alarm (item 10) http://www.realoem.com/bmw/showparts.do ... g=65&fg=60

Then you can deactivate it via SSSv32 software.

[bobw1956]

I had my Z4 diagnosed this week, cost £39 inc