What is the reason why the temperature of a certain section of the plastic extruder is high during the extrusion process?

In the daily operation of the extruder, various failures may occur in the extruder, affecting the normal production of plastic machinery. So, what is the reason for the high temperature in a certain section of the plastic extruder during the extrusion process? How to solve it?
If the temperature in a certain section of the plastic extruder is too high, the possible reasons are:
1. The fan is not working or the fan direction is incorrect;
2. The temperature control meter or PLC adjustment fails;
3. The solid state relay or bidirectional thyristor is damaged.
The main solutions are:
1. Check the fan switch and wiring;
2. Check the temperature control meter or adjust the PLC parameters, or replace the temperature control meter or PLC;
3. Check and replace the solid state relay or bidirectional thyristor.