C70 Alarm problems

been having some trouble with the alarm on the C70.

car locks and unlocks as it should with the alarm remote and arms and disarms alarm also. the problem is irratic. the car can be alarmed for any period of time then all of a sudden the alarm will go off. it doesn't matter if i park the car facing the house or facing the street.car is at least 10ft from the road on the drive and my road is not busy sometimes it doesn't go off but then other times it could be 10mins and it goes off or sometimes hours. have sat and watched the cctv and nothing around the car at some points when it has gone off. i have removed air fresherener that was inside car hanging from the rear view mirror and checked all doors / boot / bonnet are closed as should be. even tried making sure all interor lights are switched off, stereo turned off and cd cassettes removed to make sure its not a power loss problem.

firstly car doesn't seem to have motion sensors inside it. does anyone have any ideas what may be causing this problem?

have tried disconnecting the nearside wires from the bonnet catch but with this done the alarm doesn't activate the dashboard led. so reconnected it.

is there a battery in the siren for back up at all that if its failing could cause the problem? or other trigger points?

any help be very much appreciated as its no doubt annoying my neighbours as sometimes its been small hours of the morning when it goes off and i do not want to leave the car with the alarm not set.

I don't think ive ever heard my alarm go off !?!
I don't even know how to check it. LED flashes and everything and it locks/unlocks but otherwise............

Hello, I have the same problem with my C70 2.0 2002. My alarm would randomly go off in the middle of the night, without apparent reason. I discovered that the sensor is also sensitive to changes of light. On the outside of my house I have a strong light with a sensor that responds to movement. The cat would trigger the sensor, the light came on and the alarm goes off. It also once happened at my workplace as a truck shone with a bright lights over my car and the alarm went off. And of course sometimes when I leave the dog in the car when I go shopping. I solved it by switching of the interior sensor. You do this by turning of the engine, take out the keys, keep doors closed and then hold down the door-lock button and keep holding. The door lock pin will go down and then go back up after 3-5 seconds. The interior sensor is now switched off. Leave the car and lock the doors/switch on alarm. You have to do this every time you want to leave the car with the interior alarm sensor being de-activated.

I know this is an old thread, but maybe this might help someone.