Alarm triggering for no reason

[MikeV50SELUX]

Hi.

2008 MY. Recently the alarm has been triggering for no reason when locked. As it happens its being serviced Thursday so will ask them to investigate, after I've checked battery voltage and bonnet catch etc.

Question - sometimes the alarm fires with the siren (high pitched) and the horn (parp parp). Other times it only activates the siren without the horn.
Is there a difference? could that point to where the issues is coming from?... For example siren only interior sensor has been triggered, siren and horn exterior sensor has been triggered?

Advice before Thursday would be appreciated.

[Bernard46]

6 years old, probably a good chance its the standard battery leaking all over the circuit board problem in the unit that's secured under the front wheel arch, that's designed into these things. Probably £150 ish at the dealers these days.

[jeffmasson]

If you can't find a fault with the alarm make sure you have not left a phone or laptop in the car as they set my alarm off if let in the car. I think it maybe the wifi.

[mpt]

Try disabling the internal sensor and check if it's still going off, our 2005 has a button by the rear view mirror but I think some of the newer ones have an option in the menu.

We've had a similar problem with ours and disabling the internal sensors seems to have cured the problem for the moment...

[richardbr]

A common fault for the C70 was for metal (typically coins !) to set off the sensor located at the centre console. So, try seeing how you get on ensuring no coins or keys etc stored near the stereo etc.

[DT19]

My V50 has been doing this as well. Curiously it only ever happens when it's parked on the drive at home and it's never done it when I go anywhere else. I thought it was those pesky kids playing football or just rocking it to make the alarm go off but I tried switching it into reduced mode when I get home and it hasn't gone off since.

[Orca2]

My C70 has been doing this for ages we just switch the full guard off and it seems fine, I think its the alarm module as the v70 had the same symptoms, solved with a scrappy alarm box from an s80 just looking for another to fix the C 70 now.

[MikeV50SELUX]

Thanks for all the replies. Battery is not original only a couple of years old. Alarm has gone off with car parked in different places. There is hardly anything (coins etc) in it but one day when it went off 4 times in about 20 mins i did have my phone in it. I have now found the reduced guard setting in the menu and it has been ok so far. Will go back to full guard tomorrow to see if problem comes back. Will mention it at service but don't really want additional expense as 100k service and it needs new pads.

Thanks.

[Bendolfc]

Have you left a phone or tablet in there with wifi on?

Ignore that just seen your last post.