I had the dash end panel on the drivers side off last night to remove the airvent. Afterwards, when I locked the car, I could hear a high pitched noise which came and went in time with the hazard lights.

This morning the same thing happened when I unlocked the car and then, when I started the engine, the high pitched noise was back. This time it was constant and seemed to be coming from either behind the dash on the passenger side or behind the battery in the engine bay.

I drove all the way in to work and the noise didn't go away. After turning off the engine the noise persisted for a few seconds and then it went silent. After a restart of the engine it was gone (this did not happen in the morning after the engine had only run for a few seconds though. Locking and unlocking the doors still makes the noise and if I restart the car afterwards, the noise is back.

It doesn't happen if I turn on the hazards manually so it must be central locking/alarm/immobiliser related.

Where to start? ARGH! So annoying!

http://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1262446

This seems to suggest that the siren is located in the area I described above.

I'll have a go at removing that then. Possibly on my lunch hour; it seems like a quick enough job.

Here's a question; is it better to undo the bolts that hold the wing on or jack the car and remove the arch liner in order to get at the siren?

In principle you can just undo the top bolts of the wing and then bend it back a little at the top, just to remove the metal cover over the alarm system.

Note your car doesn't necessarily have the alarm in that particular position. And that it's not confirmed your problem is actually the alarm.... I'd try and really locate the noise exactly by listening through a tube first.

Good advice, thanks.

The alarm siren has never worked when I've deliberately tried to set it off so I won't be losing anything if I remove it and something else is the problem but the more I think about it the more it makes sense.

Fingers crossed it's a simple fix.