alarm

Is it going off nearly straight away or after a period of time?

Try disabling ultrasonics inside car as it says in owners book see if still going off.


Then check bonnet microswitch


That would be my first steps also battery voltage check that I ruled out door microswitches as you would notice one of those giving a door open indication or interior light staying on

The other common fault is the mercury anti tow switch which can be found under the passengers seat so I have been told its common for the mercury to stick

When you press the fob once then strait away the second time mines goes off or when it is quite windy if this happens I just press the inside button next to the passenger light to stop it happenings

If i turn ultrasonics off its fine if i dont it varys sometimes straight away it goes off sometimes it can take a while but will check under bonnet

Well from that i would say ultrasonics unit is set too sensitive.On other marques you could adjust sensitivity, whether possible on Antara i dont know.
One thing you can try is ensuring all airvents are closed on parking and see if that helps.