Reasons:
A. Deformation of thermal bimetallic sheet;
B. The fastening screws of the moving and static contact plates are loosened;
C. Moving and static contacts are sticky and cannot be opened and closed;
D. Dynamic and static contact fatigue, loss of elasticity, and poor contact;
E. The porcelain contact rod of the temperature controller is stuck by something;
Solutions:
A. Adjust the amount of deformation, restore the original state and elasticity;
B. Retighten;
C. Grind the contacts, if there is no effect, replace the new product;
E. Adjust the angle of the contact point to restore flexibility;
F. Remove some objects, and move up and down flexibly by hand press;