Standard alarm issue v50

[paddyred]

Hey guys,

Got a 08 v50 and the siren keeps going off on random nights. Doesn't seem to do it if I put it in reduced guard so I'm thinking level sensors. Is it worth whacking it on Vida and finding the trigger?

[upv5]

Getting a Vida readout is the sensible thing to do as there are so many sensors that can randomly trigger the alarm and Vida displays which one triggered the alarm on the last 10 occasions. A common one, and it happened to me, is the mass movement sensor in the roof.
A simple short term remedy is disconnect the wiring plug, you will constantly get a alarm error message on the dash but if it is that MMS sensor random activations will stop.
I got a good used one on ebay for £15.

John

[andyv40turbo]

Have a search on the Forum for similar

Do you leave your phone in the car? or electronics in the mid cubby/ drinks holder. I believe this can trigger the alarm although I dont know why!

[iainmd]

The two things I would do:

1. Use a vacuum cleaner to hoover out the ultrasonic sensors in the roof.
2. Replace the siren unit in the plenum chamber under the bonnet. Highly likely that the battery in it is failing. Common known problem on these cars after they get over 7-8yrs old.

On both our S40 and V50 we have had the issue of the alarm going off randomly (mainly when it was windy but not always). Replacing the siren unit fixed it both times.

[paddyred]

Thanks for all the replies. I need to find someone locally with vida as I don't really want to pay through the nose for Volvo to do it. I imagine it is that alarm module. I assume that the new unit has to be brand new and coded in?

[iainmd]

The siren unit isn't coded to the car amazingly. You can swap it yourself. I previously used a second hand unit salvaged from a newer model than my own but now our cars are that much older I think new is probably the only sensible option. There is a tutorial somewhere on here relating to replacing the battery in the siren unit yourself but if you aren't confident with electronics it might not be for you.

[paddyred]

Thanks! I'm pretty confident with electrics (Ex-aircraft engineer) so it may be an option. I need to check it's that first. It's not done it for the last 2 weeks though so it's seeming to be a sensor issue as a battery problem would have probably shown in the cooler weather. In relation to the sensor cleaning inside where are the sensors? I'm used to seeing a little grill near the interior light units but can't see anything?