2. Then wrap the spring around the hook, with the open end facing the switch seat, and hang the open end on the hook in front of the switch button back and forth.
3. Click to try. If you feel elastic and can keep opening and closing, it's basically ok.
4. Finally, boil the water and see if it can trip after boiling. If the water doesn't jump for a minute or two after boiling, it means that the bimetal is in the wrong position, and then reinstall it.