C5 X7 2009 alarm issues

[bigblackfalco]

I seem to have intermittent issues with my alarm going off, so need to ask a few questions for clarification.
I should point out that sometimes i don't get to use my car for a few weeks on end due to commuting by motorcycle, so to stop the battery going flat, I invested in a dashboard solar panel which gets plugged into the OBD port (between front seats). This maintains the battery at 12.5v
The car battery is about a year old.
I have been locking the car just with key in drivers door/ without arming the alarm as I thought it was the current drain from the alarm was causing an issue, but a few times I've noticed when i get back in car I have the fast flashing alarm LED although the alarm has gone off in my absence.

Does the alarm siren stay activated regardless of if its actually been armed with the key fob?

Am I correct in assuming that there is a back up battery in the alarm itself?

Could these batteries be failing causing the intermittent problems, or could it be the main battery voltage dropping overnight (in minus ambient temperatures) and causing a cascade effect with the alarm batteries?

Does anyone have any other ideas?

Many thanks

[GiveMeABreak]

So just to confirm:

• Any use of the remote fob buttons to lock, or with a second press, deadlock the vehicle will arm the alarm system.
• The only way to deactivate the alarm is to lock it using the key, not the fob, in the DRIVER'S door either once for standard locking or twice for deadlocking.
• If the alarm button is flashing rapidly on your return, then it has been triggered at some point.

As for the Siren:

The siren carries out diagnostics on its connection with the alarm unit and on its permanent supply.
If the siren detects a malfunction, the siren is triggered.

The siren has its own power source consisting of accumulators.
Charging of the siren battery is only permitted when the status of the vehicle’s electrical system is other than "Off".
If the siren supply is lost, the siren uses its power reserves and is triggered.
The siren is able to carry out 10 triggering cycles of 30 seconds when it is disconnected from its electrical supply.

Economy mode won't deactivate the alarm either.

These systems also have 'lift' protection so if the car is lifted up it will trigger the alarm. You might consider closing the air vent flaps in case the strong winds are causing the ultrasonic volumetric sensors to trigger - or disable the internal protection by removing the key from the ignition and pressing the alarm button next to the CHECK switch within 10 seconds, then getting out and locking. It will revert back to normal the next time you open the car automatically.

[bigblackfalco]

Thank Marc.
It's way more complex than I thought!
Could a BSI fault cause alarm issues at all? Is it worth a reset?

[GiveMeABreak]

The BSI talks to the alarm ECU via the CAN network, but is mainly concerned with the door / boot switches and the flashing of the indicator lights and alarm activation on the dash.

If there is a fault it will be recorded in the BSI (there are a lot of potential fault codes), so should be easy to see what the culprit / suspect area is. If you get the chance to identify them with Diagbox, let me know and I can see what they say.

There's no harm in doing a reset - but also check to make sure nothing is catching in the doors or the tailgate and that all the windows are fully shut on exiting.