Alarm occasionally goes off

[dhobbs]

What are the causes of the Z4 alarm going off?

This occasionally goes off within a minute of locking the car, but not always. Usually after I’ve driven somewhere.

I took the bonnet switch off and cleaned the contacts and the main rod/pin. This seemed to help for a few days.
I have also changed the rear level switch that’s on the rear control arm, but that was about 2 months ago so I would assume it’s not that (although I do need to check).

I ran Carly and got a code 00048 on the gateway module, which may be linked to a dodgy bulb in the interior lights.

Would an old battery cause this issue? The battery is at least 6 years old but still has the green indicator shown.

Could this also be related to a low key battery?

Thanks in advance
Daz

 

[Stuartt]

It’s most likely your bonnet switch. Unplug it for a week and see if it goes off or not.

Stuart

 

[buzyg]

Where exactly is the bonnet switch.

 

[dhobbs]

Bonnet switch is close to the bulkhead, where the two cross members meet.

 

[dhobbs]

I’ve disconnected the bonnet switch and will see if that helps.
Out of interest why is it the bonnet switch? I only ask as the only time the alarm goes off is when I lock it after a drive.
If it was the bonnet switch I would assume that would go off at anytime (which it doesn’t)

 

[Jollyjoiner]

My old E85 had the same issue, alarm would only seem to go off on the drive and mainly at night too. Disconnected bonnet switch and it didn't go off. Put new switch on an never went off again. Seems to be a common and the most likely cause.

 

[dhobbs]

How much are they?
Ones on eBay are over £30. Is that normal?

 

[Stuartt]

I’ve disconnected the bonnet switch and will see if that helps.
Out of interest why is it the bonnet switch? I only ask as the only time the alarm goes off is when I lock it after a drive.
If it was the bonnet switch I would assume that would go off at anytime (which it doesn’t)

Who knows just most of the time it is. Plenty of threads on here about it.

My theory is that due to its position it must get very hot and over time theswitch must degrade.

Yes they aren’t cheap either but it’s the same switch across the bmw range, mini too, most people just leave it disconnected.

Stuart

 

[mmm-five]

If it was the bonnet switch I would assume that would go off at anytime (which it doesn’t)

Because the bonnet switch is only armed, along with the rest of the alarm system, when you lock the car.

...and the heat from the drive might be making the switch more likely to trigger as it cools down.

 

[Lance]

Replaced my bonnet switch about 5-6 years ago, never had an issue again. Was £11 ish from a main dealer.

Pre replacement mine behaved as the OP describes. I also tried the cleaning it method, temporary fix :x

In the meantime, you can lock the car using the actual key, which doesn’t arm the alarm.

 

[R60BBA]

It could also be due to a faulty door lock actuator.

 

[Jollyjoiner]

How much are they?
Ones on eBay are over £30. Is that normal?

Can't remember but around £40 springs to mind from main dealer

 

[dhobbs]

Tbh when I cleaned it recently the plastic was brittle so best to replace.

 

[dhobbs]

Day 1 with bonnet switch disconnected. All good.

 

[Timmyboybunter]

Mine has been intermittently going off since I bought it a year ago - a couple of times a week, to the point where I needed to leave it unlocked as it was annoying everyone.

Not the bonnet switch - that was unplugged on week 1

I disabled the tilt alarm and internal sensors about 3 weeks ago and it hasn't gone off since - so one of those 2 is my culprit.

 

[dhobbs]

How do you disable the tilt and internal sensors?
Is that by locking the car with the key in the door rather than the remote?

 

[R60BBA]

Mine has been intermittently going off since I bought it a year ago - a couple of times a week, to the point where I needed to leave it unlocked as it was annoying everyone.

Not the bonnet switch - that was unplugged on week 1

I disabled the tilt alarm and internal sensors about 3 weeks ago and it hasn't gone off since - so one of those 2 is my culprit.

So if someone breaks into your car what happens?

 

[oldgitdave]

How do you disable the tilt and internal sensors?
Is that by locking the car with the key in the door rather than the remote?

Lock using the remote but press the lock button a second time within a couple of seconds or so. The clowns nose led should flash rapidly for a few seconds to indicate the internal sensors have been disabled. Alarm should still go off if someone forces open a door, bonnet or boot.

 

[Timmyboybunter]

How do you disable the tilt and internal sensors?
Is that by locking the car with the key in the door rather than the remote?

No - though the reply from Dave above I've seen mentioned in various places, but I don't want to be doing that every time; there's an option in Carly to disable the 2 sensors.

So if someone breaks into your car what happens?

Contact points will still be active, so if someone opens the doors/boot (but not the bonnet ) then the alarm will sound - but yes, if someone smashes a window and climbs in Dukes of Hazzard style then the interior monitor sensors will no longer trigger the alarm.

 

[Malamutalisk]

I’ve got this same issue. Mines started going off randomly once a week. I’ve read that if you put something on for extra pressure pushing down that helps?

I’ve tried making this tonight. Bit of hard plastic between two cardboard pieces, superglued together and onto the top of the bonnet switch. I’ll see if that works... if not is there any harm in just disconnecting it? It’s not going to drain the battery or anything?...