My alarm keeps going off on my audi a3 1.9tdi 55 plate, it doesnt sound like the normal alarms which come off the horn its more high pitched,i have tryed double locking the car but its still goes off when its not locked its ok

try making sure the heater air grills are closed as air movement ie windy night ,could set of some alarms , i'd also check for voltage drop as this will set alarm off , also check battery holds the charge as may disperse just enough to set alarm off but not so much to be a problem when starting , YET .

Depending if it is a aftermarket or a factory alarm, they should all have fuses that can be removed. By removing the fuse, you may lose your keyless entry option. Most aftermarket alarms have a siren that is usually mounted under the hood in the engine compartment area. I've seen where people have cut the wire going to the siren to disable it but keep the power going to the alarm system to keep the keyless entry still functional if it came with the alarm system.
Factory alarms usually use the existing horn for the alarm. If that is the case, you might need someone who is experienced to disable the circuit so that the horn will not sound if alarm goes off but the horn will still be functional when needed. Hope this helps.

For starters first check the wire going to the horn, it may be cut.

try disconnecting the battery and reconnecting

Is this a factory alarm or a add on weekend boy racer type thingy ,if the later cut it out the system as they always go wrong when they get old

pressing lock button should activate alarm sound. system, when you press unlock button that deactivates alarm sound.i you dont hear alarm sound problem is in the ecm.

You probably have a faulty door,boot or bonnet lock.If you put the inside light switch to the setting for the light to come on when the doors are open,close all the doors and see if the light goes off.If your model golf has a display on the dash,it shuold tell you which door is open.It could also be a faulty interior sensor or a faulty alarm horn.A diagnostic machine will be able to tell you which was the last alarm activation.

There is a few things to do check the door switches that control dome lights, check wire down by the skid plate when you get oil changed there is a sensor for the starter there if it is stolen the alarm will go off or just take a BAT and BEAT the living **** out of your horn and call it good like I am going to. I hope this helped or will help I recommend an aluminum bat vrs. wood

this sounds like a faulty 'boot' switch. Many of the older models had issues with picky switches

i had the same problem with my 2001 audi a6 and just foung that if i left the windows cracked at all it would do it so make sure all your windows and sunroof are all the way closed see if that works if not then take it in to the dealer ship sounds like you might have quite an electrical problem.