Fiat Punto Active '04 Central Locking problems

My car has recently started unlocking itself in the middle of the night or when parked up. I have had it back to the garage numerous times but as it
is not faulting when at the garage they are telling me there is nothing they can do.
It started about a month ago when i noticed the drivers side was locking but the passenger side wasn't, then the locks started springing up as soon as i turned the key, and now it is just randomly unlocking itself as and when it pleases.
Just wondered if anyone has any ideas as to what could be the problem as my garage have proved to be useless up to now!
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Not a hundred percent sure? but it could be the solenoid on the central locking module. If it is that, you need to eliminate each one until the problem stops.then its a just case of getting a new central locking module form a salvage yard are a new one? the garage I thought should have done this and checked them out for you? like i said not a hundred percent sure.

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Hi
My Punto 2001 HLX has developed a similar fault. Sometimes the 'door open' warning light comes on when you're driving causing the interior light to come on (most disturbing at night!), then it corrects itself. I've discovered it can happen if I brake hard.
What is worse is it's not possible to lock the car when the damn thing is in this mood. I took it to my local Fiat dealer and they've never heard of it. I booked it in for them to check it out but within 10 minutes the fault had gone away. The (helpful) engineer said the central locking could have it's own fuse so it's possible to deactivate it so I can at least lock the car manually. But it's so erratic it hasn't seemed worth doing yet.
Until I have a permanent fault which they can investigate I'm going to have to live with it. But if anyone can throw any light on it (not my interior light) I and I'm sure Sarah would be most grateful.
Thanks in advance for any help given.
Rick

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If it's an RF system there have been many reports of radio interference causing intermittent faults often in a specific locality. Problem is you can never locate the source, though mobile phones and masts are believed to be implicated. In cold weather and ungaraged cars, condensation on electronics boards and components is another possibility.
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