Alarm / Central locking issue

[TheT6Kid]

I have read all of the posts i can find on the forum about alarm issues and I am almost 100% that i will need to replace the alarm siren module.

Could anyone suggest anything else prior to buying the kit?

Without notice after a long very wet return down the A1, the alarm went off after moments of parking and locking the car. It now goes off intermittently when it feels like it. I have tried parking it with the interior sensor disabled - no difference.

I do not have any service messages other than the normal Alarm triggered - check car after turning ignition on,

I have adopted locking the car with the key therefore the alarm not getting set - this results in 'alarm free' nights of sleep.

I have returned to the car a couple of times and found all the doors except the drivers door unlocked. Only since this problem started.
I have locked the car with the key and waited about 30 secs until you get the second 'clunk' which i presume is the deadlocks engaging.
It seems to be at this point that the rest of the doors unluck. However I cannot be totally sure as i have only seen this once.

I found a procedure for a UEM reset in one of the threads and did this today, I also give fuse 8 (rear fuse board) a good wiggle as this is mentioned to be the fuse for the alarm.

Any suggestions would be useful, i intend to use the alarm as normal during the day to see if any of the above actions have remedied this, other than that does anyone think the central locking issue is attributable to the alarm siren module dying?

[M-R-P]

One thing to note is the bonnet latches, I think they are both attached to the alarm system, May be worth blasting them with WD40 to get any water out. Although, I don't think water in the bonnet latches would cause the car to unlock. Are you sure all the doors lock with the key and not just the drivers door?
Another common fault is the alarm module itself. The internal battery leaks after a few years and corrodes the connections inside the module, sending it doolally or, like mine, just disabling the noisy bit.
Hope this helps.

[TheT6Kid]

Yeah 100% they all lock initially. Maybe some WD40 in all the mechanisms may help, I'll give that a whirl as well.

[M-R-P]

Good idea, if the problem started after a wet drive then that could be the source of the problem. Multiplexed wiring - sending loads of signals down a few wires, the slightest bit of moisture in the wrong place causes havoc! My mate had a clio cup that had a similar problem - lock the car and all the indicators would flash or the horn would go, use the indicators and the alarm went off etc.
When you buy an alarm kit for volvos, they often come with bonnet catches as these are known to be a problem.

[TheT6Kid]

I'm gonna tempt fate here. But since I took the remedial actions listed above. The problem seems resolved!

No unlocking, no false alarms!

Hope I haven't spoken too soon.

[TheT6Kid]

Good idea, if the problem started after a wet drive then that could be the source of the problem. Multiplexed wiring - sending loads of signals down a few wires, the slightest bit of moisture in the wrong place causes havoc! My mate had a clio cup that had a similar problem - lock the car and all the indicators would flash or the horn would go, use the indicators and the alarm went off etc.
When you buy an alarm kit for volvos, they often come with bonnet catches as these are known to be a problem.

Just noticed where you live, I'll be in Poole in September at the RNLI College! Sadly I'm likely to be in a non Volvo hire car!
I like Poole, it's a great place, at least it is for me as a visitor! Stayed in Weymouth for hols a couple of years back too.

[TheT6Kid]

Got 4 - 5 days out of it but fininshed nights this morning and it's gone off 4 times in a couple of hours!
Coincidently its been raining!

[M-R-P]

Process of elimination then, Do one bonnet catch - see if it changes anything then try another till you find the culprit.
Good luck.
P.S. That RNLI college is the bogs dollocks, took the little one there to watch the indoor simulator thing - awesome!