Alarm issue

[CHIMV8]

My mates Z4 alarm goes off for no reason

He leaves the car at his caravan during the week obviously locked.
It can be ok for a few days,then the alarm sounds,so he now leaves the key with a neighbour so it can be turned off

Any suggestions as to why and remedy

Or can someone explain how to disconnect the alarm altogether please

Does it have its own fuse that we could pull out

 

[Lance]

Sounds very much like the bonnet sensor. Open bonnet and look middle up near the bulk head. You can clean the switch up with something like WD40, however IME it just starts playing up again. For £20 ish pounds and two mins to unplug and change, a new one makes more sense.

Other option, key in door and lock manually, then the alarm doesn't arm.

 

[Ducklakeview]

Bonnet switch a common fault - Try unplugging it and seeing if it cures it. I bought a new switch and it also failed, couldn't be bothered taking it back so left it unplugged.

Mike

 

[Beatman]

I had a similar issues, and as mentioned by other members. It turned out to be the bonnet switch.
Disconnected it and the fault went away. Refitted a new one all is ok

Ps I had to adjust the bracket slightly, as I didn't think the switch was being depressed fully when the bonnet was closed.

 

[CHIMV8]

Cheers guys appreciated on my way to sort

 

[Z4 COUPSTER]

As all above. Mines be disconnected for 3 yrs, as I have been waiting to get a new one.
Btw the new one will never arrive.

:roll:

 

[noiseboy72]

Not quite the same issue for me - and I have cleaned up the bonnet switch, but my alarm sounds about 30 seconds after arming. Happens about 75% of the time. If it sets OK, then it doesn't go off again until I set it again.

Is there any other common failure points for me to look at?

 

[mac27040]

could be your tilt sensor, you can deactivate that through coding.

 

[Jembo]

Not quite the same issue for me - and I have cleaned up the bonnet switch, but my alarm sounds about 30 seconds after arming. Happens about 75% of the time. If it sets OK, then it doesn't go off again until I set it again.

Is there any other common failure points for me to look at?

Have you tried disconnecting completely?

Cleanings not the issue, as when worn it’s the contacts that connect... removing it (to test) will tell you for sure

 

[noiseboy72]

Thanks, will remove and bypass it. I assume it needs the contacts to be closed to arm?

 

[Jembo]

Thanks, will remove and bypass it. I assume it needs the contacts to be closed to arm?

Nope...

The contacts are supposed to be apart when it arms. Should someone manage to open the bonnet when locked, the spring catch closes the circuite & sets off the alarm... so when the switch is faulty, the circiute’s still closed hence the issue why alarm goes off.

By removing the pressure switch altogether, the circuite remains permanently open... ultra simple job to unclip, just take your time to gently wiggle free

 

[Adam D]

Just had to change my bonnet switch for the same problem, new part was £30 from bmw and so far all is good. Ten mins to swap them over.

 

[noiseboy72]

Thanks all, hopefully fixed now, time will tell!