In the last few weeks the alarm on our vRS LE has decided to start wailing somewhere between 2am and 4am.

It's not every night, and the weather outside varies (sometimes rainy, sometimes not, sometimes above freezing, sometimes not) - but it is doing my head, let alone the poor neighbours.

Is there a common cause for this?

Please help before I lob a brick through the window to give it a reason to go off....

Make sure your bonnet is closed properly. Mine was doing it too. Turned out the catch on the bonnet needed greased.

Spiders.

Little pesky ones that crawl around near the sensors

Spiders.

Little pesky ones that crawl around near the sensors

Spiders love the gap at the front of the car behind the grill, sady i don't love them very much :(

Ensure your boot catch is not sticking also. This is a common cause for random alarm triggering even though the boot is shut!

My mums Celica used to do this, again it was a spider causing the issue.

Right, will check boot and bonnet catches and pressure wash the front of the car to remove spiders!

My Bonnet latch's microswitch had actually failed.. Easy way to test the theory.. Disconnect it, it's a "make when opened" circuit, strangely.. so disconnecting it makes it think the bonnet is closed.

You'll notice, if it's failed, that you don't always get the single light flash on locking. It's normally accompanied by the intermittent wipe working, well.. intermittently, lol!