Can anyone help, I'm having problems with my alarm for the audi A3 FSI, petrol on a 04 plate. The alarm keeps going off at various times, not consitent. The alarm sounds but the lights do not flash, there is no evidence of an intruder and the alarm will go off at any hour day or night and sometimes more than once, even though its been reset.

 

Check the function of all door locks (locking, unlocking, etc.). If any do not operate properly via the remote than there is probably a microswitch inside the actuator that has gone bad and is not communicating the proper open/close(d) status to the central control module.

Check that the puddle light in each door does not remain on even after the door is closed. If it does, it may indicate a bad diode in the puddle light, causing problems.

Is your battery voltage low? this may also cause issues.

Check hood trigger.

Do you have after-market radio? There is a radio trigger too, but this is unlikely unless it is coincident with new radio install.

Trunk/liftgate also has failure prone microswitches in the actuator.

Lastly, it could be the central (comfort) control module, but this is a worst case scenario, and is usually accompanied by other symptoms such as intermittent interior lighting failures, lights that won't turn on or won't turn off, etc. If there is water ingress into the CCM area there may be a portion of the circuit that is pooched, or a wire in the vicinity that is bare and grounding, or disintegrated.