V70: Electrical Alarm Going off infrequently

[Topper]

Have 2008 V70 D5 - had car 3 months and during that time, alarm has gone off without reason (?) about 6 times - each time seem to be when external temperature has changed i.e. during night when it freezes / thaws or when early a.m. sun hits car. Also this week, on a cold a.m., key fob remote wouldn't open car ... got spare and it worked... any connection ???.... now have replaced fob batteries.

"Reduce Guard" setting - set earlier this week in case movement sensor was playing up, but apparently no effect.

Last night alarm went off at midnight when cold weather thawed. Have checked with local Volvo dealer ... won't comment but they want £ 86 diagnostic check plus repair.
Local car repair company says possible solder joint expanding / contracting .. they don't apparently want to attempt and to go to Volvo ?????

Low battery ...did seem loathe to start one morning recently ... possible answer ???? ... bonnet catches ( checked - they seem tight )

Any other ideas besides Volvo dealer getting more money ???

Does alarm system have fuse, enabling it to be disabled ... checked manual and there is a fuse for Alarm Siren / Electronic Climate Control but will I disable something else if I remove this ??... or is it connected with central locking?

Topper

[tommyweaves]

It might be worth having a check in the 00-07 forum, whilst that's the previous generation V70 to yours there are a lot of posts relating to common issues such as knackered battery that may relate to the newer V70s. Just a suggestion!

[Topper]

Sorry for the delay ... thanks for that ... there are certainly a few possiblities in that area ... the most likely seems to be , if main battery O K ........replace alarm siren ... therefore be interested to know :

1. If the alarm siren on the upto 2007 model is the same as on my 2008 onwards version .. and if location is same ...?
2. What else will I lose by removing Alarm Siren Fuse ?

Any help / suggestions would be appreciated.

Topper

[Thassos]

A few other things that might be worth checking.. yours being relatively newer would have thought less likely to be battery (either in alarm module, or main battery related), but then again battery troubles do tend to occur with low temperatures. Have you measured the main battery voltage after a period when alarm has been on, say on a cold morning ?

1- A moth or spider, these can sometimes set off ultrasonic alarms and although this theory sounds simple is worth a look for anything inside the car that can move on its own steam !

2- Air pressure affects speed of sound through air, and ultrasonic sensing (i think !) this is why you see people leaving sunroofs or windows open in windy weather and the sudden change in air pressure can cause alarms to go off..

Have you tried disabling the interior movement sensor? (not sure if yours has a button on the dash, you press this before exiting the car/locking and it leaves the ultrasonic/interior sensor off (i think also the car movement sensor off) and leave the car locked like this to see if still goes off.

The solder joint theory is a possibility, i think the alarm module on the P2 cars is in the centre of the roof, you could maybe remove it and have a look at the condition of its soldering ?

Well thats my 2 penneths.. hope its useful

[Topper]

Thanks Thassos - yes, disabled interior sensor and still have it disabled ... but it went off the second night I had it disabled .. obviously not that.

Haven't had the alarm running for that long !!!! ... had to switch it off before the neighbours put my windows through so not checked voltage.

Thanks for the info .. would love to know about the Alarm Siren fuse and what other items could be disabled as a result

Topper

[D5driver]

Find someone local to you with VIDA and get the codes read. This will tell you the reason for the triggering of the alarm

[Thassos]

Just a thought, along the lines of maybe some local RFI interference, are you parking it in same location or could there be some local strong RF signal such as a radio mast, mobile mast or similar?. A lot of this stuff is hidden in signs or not exactly visible.. such things can drown your remotes signal and hence you would see problems unlocking etc (or did replacing the remote batteries result in a much better distance from which the car locks-unlocks? - kinda indicating its the fob's batteries contributing to the problem..)

[Topper]

Thanks again ... sorry for delay, been away ... replaced fob batteries and they work better and from a longer distance ... no local interference to the best of my knowledge ... always parked in same place in my driveway (as was previous V70) and 'er indoors car .. never a problem.

Any views on the comment in the manual .. lock / unlock 3 times to re-set .... ????