I have a switch under the dash that Im not quite sure what it does. I have an 07 XLT supercrew. Has the factory alarm I imagine. My brother has the same year, but no switch. Doesn't seem to do anything, tried to trace wires, the seem to join up with some other wires under neath the steering console area.

Here'a a pic:

http://dl.dropbox.com/u/8102696/photo-1.JPG

 

Does not look OEM.

 

I'm with 60DRB...it's NOT an OEM switch. It's likely an aftermarket alarm switch, or it could be tied to auxiliary lights.

 

I may be wrong on what it actually is, but I call it a valet switch. If for some reason you set your alarm off by accident you will have to push this to reset it as well as get it to stop the alarm before you can start the vehicle. I once set mine off by showing off my remote start (forgot the ECM had a code which will not let truck start by remote) and pressing the buttons to many times, and causing the alarm to go off. Very embarrassing moment by the way.

 

I'm with you, looks like a valet switch to me. Easiest way to check is roll the windows down, lock the truck (to set the alarm) reach in and open the door from the inside (to set the alarm off) then hit the button to see if it kills the alarm.

 

I may be wrong but believe it is part of a viper system? I have seen them also. A small size toggle switch just hanging there.