The trigger on your Xbox 360 controller has various functions, primarily being used to fire weapons in various fighting and war games. This trigger is an integral component to the controller. So if you have found yourself with a damaged trigger on your 360 controller, you may be thinking that there's no other option than to toss it out and buy a new one. This isn't the case, as it's possible for you to open up your 360 controller and fix the trigger yourself.
Unplug your 360 controller from the port in the front of the Xbox console and place it face down on a sturdy work surface like a table or desk.
Unplug the battery unit from its port in the back of the controller and set it aside.
Use your Phillips screwdriver to remove all six exposed screws located on the back of the controller and set the screws aside. Then remove the single screw in the battery compartment and set that aside.
Lift the back half of the controller from the front half and set it aside. The green circuit board and triggers will now be visible in the front half of the controller.
Fit the lose trigger back over the spring it connects to. When it snaps in place, you'll know it's secure.
Replace the back housing and screws of the controller. Your triggers should now be working without any problems.