Car Alarm Goes off Randomly even after fuse was removed/How Can I permanently disconnect alarm

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2001 Audi A4 1.8T Quattro. Also may it be related to same car going into a deep puddle of water ( road was dark ). It was towed to nearest mechanic, where “engine was flushed”, and I was charged $250. What does an engine flush entail? and how can I best disconnect the car alarm?

Is it a factory alarm or an aftermarket alarm? Does it have it’s own horn/siren or does it use the cars horn?

I believe it is factory, I just bought the car a month ago. It does not seem like it is the horn, how could I determine?

Just so that we are all on, “the same page”, so to speak…
When you say that the alarm “goes off randomly”, do you actually mean that it goes ON randomly?

Open the hood when the alarm is sounding. Locate the source of the noise. It’s usually a siren mounted on the inner fender. It will have some wires. Disconnect them…