Car Alarm Activation

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Patty
Joined: Thu 09 Feb, 2012 15:55
Posts: 38

  Z3 roadster 1.9i
Location: Wigton

Car Alarm Activation

Post by Patty »

I'm experiencing issues with my car alarm activating shortly after I've locked the car. Had a run down to Keswick today with the roof down in glorious sunshine and clear blue sky's. Parked in Booths supermarket car park, locked car and alarm set, when I returned 1 hr later the side indicators were flashing. I appear to be getting this problem whenever I lock the car, Has anyone any experience of a similar fault, should I be able to identify the problem area using the PC diagnostics. I'm fortunate in having someone with access to the diagnostic tool is this the way to go?
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Brian H
Joined: Tue 16 Dec, 2008 19:55
Posts: 2505

  Z3 roadster 3.0i

Re: Car Alarm Activation

Post by Brian H »

Patty,

There are a couple of sensors that spring to mind that you can check, IIRC these are on the same circuit.

1. The bonnet sensor
2. The radio sensor

If either of these contacts are not closing properly then this can cause false alarms.

Q. When you lock the car do all the locks close i.e. both doors and boot?

Brian
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2225

  Z3 roadster 1.9

Re: Car Alarm Activation

Post by BladeRunner919 »

Most common issue is the bonnet sensor. Easiest way to test is just to unplug it and see what happens. With the switch unplugged the alarm sees it as 'bonnet closed' so is perfectly happy. I gave up trying to fix the switch and just leave it unplugged.
Patty
Joined: Thu 09 Feb, 2012 15:55
Posts: 38

  Z3 roadster 1.9i
Location: Wigton

Re: Car Alarm Activation

Post by Patty »

Brian
thanks for the tips, I checked the door and boot locks and they are definitely locked, I'll probably be able to check the bonnet switch but can you expand a bit on checking the radio please.
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2225

  Z3 roadster 1.9

Re: Car Alarm Activation

Post by BladeRunner919 »

Patty wrote:Brian
thanks for the tips, I checked the door and boot locks and they are definitely locked, I'll probably be able to check the bonnet switch but can you expand a bit on checking the radio please.

There's a sensor that is triggered by the radio being removed. If you have an aftermarket radio the sensor needs to be bypassed. But unless you've changed the stereo recently, I'd start with the bonnet switch. Apart from anything it takes about 30 seconds to unplug, whereas messing about behind the stereo will take somewhat longer.
Patty
Joined: Thu 09 Feb, 2012 15:55
Posts: 38

  Z3 roadster 1.9i
Location: Wigton

Re: Car Alarm Activation

Post by Patty »

Thanks for that Brian, I'll give it a go in the morning let you know how it goes.
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knoxvillain
Joined: Mon 27 Aug, 2012 11:05
Posts: 43

  Z3 roadster 2.0
Location: Edinburgh

Re: Car Alarm Activation

Post by knoxvillain »

I had this. Opened the bonnet and closed it again and all fine. :)
cooknerkid
Joined: Sun 05 Aug, 2012 15:30
Posts: 48

  Z3 roadster 2.8

Re: Car Alarm Activation

Post by cooknerkid »

My alarm was also going off in similar circumstances, and I had already tried the aforementioned routes, but thanks to this site, i was advised that it could be an internal sensor, so by double clicking the key fob, watch the LED between the seats remain on for 2 secs, and when double clicked havent had any issues, so from that we could deduce that it was an internal sensor-- Since then I have been to local Indy to ''clear'' the alarm activations on the diagnostic machine, so that when we look at it next, we will be able to isolate which internal sensor is playing up .. No doubt it will be the expensive bit under the tunnel carpet!!!
Kevinuk
Joined: Wed 01 Aug, 2012 20:01
Posts: 27

  Z3 roadster 3.0i

Re: Car Alarm Activation

Post by Kevinuk »

Hi...I had exactly the same problem

Disconnected the bonnet switch and that solved it ..I think it is quite common
RichP
Joined: Wed 20 Feb, 2013 00:47
Posts: 190

  Z3 roadster 1.9

Re: Car Alarm Activation

Post by RichP »

I had a problem with my alarm going off, not certain its related but the problem went away when i fixed the boot wiring loom.

The wires running from the back left side of boot opening to boot lid were broken and forming erratic connections. The boot lock would intermittently work and not work and the boot brake light also didn't work. I've wired in a new section of wiring and everything seems to be fixed, and the alarm hasn't gone off since.

My guess is that the loose connection was setting off the alarm. I'm sure someone here can tell me if it was more likely a coincidence, but its something to check.
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"I spent a lot of money on booze, birds and fast cars. The rest I just squandered." George Best
Patty
Joined: Thu 09 Feb, 2012 15:55
Posts: 38

  Z3 roadster 1.9i
Location: Wigton

Re: Car Alarm Activation

Post by Patty »

Hi Brian and others who responded to my alarm problem. Followed Brian's advice, disconnected the bonnet switch connector and checked with a meter for operation of the switch. Found it to be open circuit with the bonnet effectively open and closed circuit with the switch armature pressed in. Following doing this the problem has gone away.
Learned something else about the Z.
Thanks again to all who responded.
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