Where is the Lid Switch? Acer Aspire5315

Hi,
I reinstalled the lid on my laptop because I just moved below the false floor.
The lid is empty (no LCD panel), no connectors connected to the mainboard and still it is detected when closed.
I have the wiring to the power switch on the dashboard, and that doesn't work when the lid is closed (it's natural as one couldn't even reach the original power button with the lid covering it)
I would like to deactivate the sensor, I just can't find it, as it may not be mechanical, more like hall, or maybe proximity sensor.

Does anyone know this model, or similar one?
Thanks!

Display properties/Screen Saver/Power/Advanced - When I close the lid... - select "Do nothing".

Still, I would like to know how it detects the lid position with no apparent switch.

any magnet in the lid casing? that's how my eee pc does it. some chip that senses the magnet on the main body.

@mkl: setting the lid action in OS, defines only the behavior when closing. Hence the option in OS "when I close the lid", not "when i open it"... My laptop doesn't resume from standby/hibernation/power off when the lid gets opened. Furthermore, when the lid is closed, the motherboard doesn't accept commands from the power button... the lid MUST be open. So this is not controlled by the OS.
Otherwise, hooking up the lid switch to the ignition would've been an easy way to make a poor-man's-shutdown-controller.

@all: after experimenting with the dismantled laptop, I found that a lid sensing is only triggered when the lid's hinges (they're metallic, so they conduct electricity) are in contact with their base on the laptop. The hinges connect to a thin foil glued on the inside backplane of the lid... this foil gets detected, but ONLY when it's connected to chassis ground.
So I insulated the foil from the hinges and presto: the lid can't be detected any more.
http://www.postimage.org/gxaor69.jpg

The theory behind this? I really don't know... proximity sensing? HALL effect? capacity between a sensor and the foil? something like that.

Thanks for the advices!