Alarm goes off on its own
 

My saloon alarm keeps going off completely at random - e.g. it can happen once in two weeks or several times in one day. It usually happens when the car is locked but it's also done it when the car is unlocked.*** In all cases the key fob is nowhere near the car.

Once the alarm has gone off, pressing the unlock button on the fob, then the lock button, causes a 'something is open' single beep.

I've tried a 60-minute battery disconnect but it still happens.

:shrug:



*** I have to disconnect the battery every evening to be 100% sure it doesn't go off in the middle of the night.

Could be the bonnet switch? Rubber covered button next to the anti freeze label, can be affected by water ingress or the bonnet isn't closing tightly enough. Try lubricating the bonnet catches and adjust the bonnet stops (rubber buffers either end of the slam panel) by turning them clockwise.

The bonnet switch looks fine to me - the rubber cover is intact and the surrounding area is dry as a bone anyway.

I'll try tweaking the stops down a tad just in case but the trouble is I can't tell if anything I do has worked or not without waiting weeks (the alarm has only gone off once in the last two weeks).

The water tends to get under the rubber cover rather than through any damage to it. You can remove the switch to check it for water damage by using a credit card or similar, slip it under the rubber cover either side to release the spring catches on the switch.

Ok, thanks - I'll take it off and have a look.

Btw, forgot to say I've got both interior light clusters disconnected - I wonder if that could confuse the alarm system.

I had something similar going on with my Tourer when I got it a year ago. Alarm kept going off - I too ended up disconnecting the battery at night.
Mine turned out to be door wiring.
Even with all doors shut dash often said one was still open. My mate who works in a garage selling second hand cars said he'd had this with cars before. He fixed mine in a couple of minutes. All he did was go around each door,open the door and wiggle the rubber grommet between door pillar and door about,moving the wires about a bit I guess. When he did this to the drivers side rear door and shut that door,the door open icon on dash went out and the alarm hasn't gone off on it's own again since.
Might not be that on yours but worth giving all the wires between doors and door pillars a wiggle. Paul

That sounds like a likely candidate - I was beginning to suspect the doors anyway, even though I don't get the 'door open' warning light on the dash unless one really is open. I'll take a look at the grommets. Maybe there's a sensor on each door lock mechanism too - I don't know.

The other one must be the 'boot open' switch, although I must admit I don't even know where it is (mine's a saloon).