On my montego the keyless entry pad doesn't work, it doesn't even light up when you touch a button, what can be wrong?

 

Per FORD Motor Company --
Before doing ANY electrical work, disconnect the NEGATIVE battery terminal.
On to the problem--
First, find and check the fuse -- replace with proper size fuse, if necessary.
Check keypad operation before proceeding.

All of the electrics for the keypad are inside of the door.
Check U-Tube videos for replacing the keypad on your year/make/model.
New keypads can be had at RockAuto.com or Amazon.com
But before you spend any money, make sure that your existing wiring is properly insulated and all systems are GROUNDED.
Good Luck !!