1998 Lexus LS400 Alarm Going Off Randomly

[Oldfatty]

Hello
The ear-splitting factory alarm on my 1998 LS400 has been going off inappropriately for a few months now. This usually happens just as I lock it, but not exclusively, or when I switch the engine off. It does not immobilise the vehicle (can be driven with the alarm still sounding) and can only be stopped by unplugging the battery. So far I have dialled down the proximity sensor underneath the centre armrest and changed the batteries in the fobs.

Since the alarm doesn't have any noticeable effect other than deafening me, my next move will probably be to find the siren and unplug it (not sure how this will go)

Any advice would be much appreciated
Thanks.

[GreenV8S]

Check for bonnet/boot switches - if present, check they're operating consistently and the wiring to them is sound.