I have a V70 MY2008 and the alarm started being triggered at random times. It got so bad that I had to park in distant corners of the car park at work to avoid annoying people. Every day I would come back to the car with the alarm LED blinking.

Interestingly, the issue was much worse on warm sunny days. When the car went for a service, the computer traced the problem to the n/s rear door lock triggering the alarm, and they wanted £350 for a new lock. This, as it happens, is the least used door in the car. Using a Haynes manual I dismantled the rear door (much easier than I was expecting) hoping the get to the door switch. It is buried in the lock mechanism and needed more destructive dismantling than I was prepared to do at the time - so I took the route of spraying the switch with contact cleaner and manually worked the switch many times.

Reassembled - no alarms for over a week! Then, twice in one night. Frustrated, I decided to silence the alarm. Pulling the fuse is no good as it knocks out the climate control too, plus you get a message saying 'alarm service needed'. Thinking the siren was in the wheel arch, I looked but it was not there. Setting it off and searching - discovered it under the scuttlebox cover at the base of the windscreen.

To get at it, remove wiper arms, pull rubber seal off the leading edge of the plastic cover, remove the 6 plastic fasteners (pull the centre part out - they are a bit like a rawlplug with a peg in them), remove the plastic cover and the siren can be found under a black protective cover, almost behind the battery. On mine there is relay box fitted above blocking access, but this easily clips out.

Disconnecting the siren in situ is not easy as the connector clip is deep in the unit. Use spanners to remove the black protective cage and the siren itself. Now you have a better angle of attack on the connector, use thin flat screwdriver the release the clip.

Opening the unit proved too difficult for me, so I resorted to cutting out the siren 'speaker' grille revealing a black speaker underneath. Cut this out with a blade, disconnected the 'speaker', reassembled it using silicone to keep it sealed. Reinstalled - all fine and no warning messages.

If the alarm is triggered - all that happens is the hazards flash. No 'service' warnings etc.

Maybe I was too rash in taking out the siren - I found a big fly hiding the car two days later - the culprit for the night time alarm?

The work on the door seems to have worked - I no longer get alarm LEDs when I return to my car.

Hope this helps folk with similar issues.