Alarm activating everytime the car is locked

So it seems you made a huge mistake in the first post when you said that it goes off even with the key:

Evening All

For no apparent reason, the alarm on my TD5 is going off after 10 seconds from locking it using either the fob or key. The dashboard alarm light seems to rapidly flash as soon as it's locked all the time.

Could this be a "one of many things" problem? I've opened and closed all the windows and doors, including the bonnet, but the alarm still activates after about 10 seconds.

The engine starts ok and the dash alarm light goes off when the ignition is turned on.

Cheers

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if it doesnt go off with the key it means the problem is with the volumetric alarm and all this discussion was in vain...i wanted to double check that cos if you lock with a door opened even with fob the volumetric alarm is inactive but it becomes active if you shut the door after that..., if there is a problem with the ultrasonic sensors it can be intermittent too so or plug in a tester and disable the volumetric alarm cos it's possible or unplug the sensors as @listerdiesel told you and for my shame i contradicted him based on your statement(i apologise for that)... no poroblem, it happens but at least we know now how important the details are when it comes about the alarm

When I first had this issue, the alarm was going off regardless whether I used the key or fob.
Now, with the bonnet switch disconnected, I can lock it with the key, but the alarm still goes off if I use the fob to lock the car.
I did not give incorrect details in my first post, I gave you the facts right from the start.

then connect back the bonnet switch and use the key ... see what happens, or do that test with the door open - lock with fob - wait to see if it goes off or not- shut the door... if it doesnt go off with key or with door opened but will go off after you shut thendoor it's the volumetric alarm, if it goes off locked with the key or with door opened i'm affraid you'll have to replace the BCU

i'm really trying to help you but all the informations must be 100% accurate otherwise it's hard to figure things out cos that system is extremely complicated...are you sure you didnt push accidentaly the fob button too when you locked with the key and the alarm went off? ...how many times did that happen( to go off locked with the key?) that's extremely important

My issue was fixed by disconnecting the volumetric sensor above the passenger front door.

so what's your conclusion though? .... cos nothing is ''fixed'' imo, it's only a partial cure of a symptom, like when you swallow a painkiller for a chronic pain, it would have been the same if you unplugged the other ultrasonic sensor as well or disabled the volumetric alarm for good with tester, good luck from now on m8, i rest my case