Blower motor does not work all the time

Hello,

This issue could be due to an intermittent connection issue, faulty blower motor resistor or a failing motor.
It can also be a bad connection on the blower motor switch.

First check the wiring for the blower motor. Look for any corrosion or pulled out pins.
Faulty resistor sometimes will have burnt pins.

https://www.2carpros.com/articles/how-to-check-wiring

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.