Unscrew the Tailcap
Gently pull the rubber cap
Use a thin object that is blunt (like a wooden stick) To push the Switch out of the Tailcap
Remove the switch from the plastic housing
The resistance is very high. The switch needs to be cleaned
Now let's repair it
disassemble the switch using a thin tool as shown
Clean all the metal contacts inside the switch
Removing the dirty/corroded layer
don't over do it
After cleaning the contacts, reassemble the switch as shown.
The resistance became low (0), which means it is fixed.
*Comparing a brand new switch to the fixed switch*
so, the repaired switch is as good as a new.
Now insert any switch into the housing and reassemble it as shown.
If you find it difficult to repair the switch then you can buy a set of replacement flashlight switches (link in description)
Make sure to measure the size of your flashlght switch before ordering one. The most common sized are 17x12mm and 12x08mm