A/C fan works only half the time

Welcome to 2CarPros.

Honestly, the only way we can determine what is the cause is to check when it isn't working. What you would need to do is check at the fan motor to see if there is power to it. If there is, then the fan motor is going bad and failing. If there is no power, then we will need to backtrack to the resistor, relay, switch and so on.

I attached three pictures below. The first one shows the blower motor assembly. It is behind the glove box.

The next two show which wire should be getting power when it should be running. There are two different types of motors that could have been used. You will have to use the pics I attached to identify which one you have.

Using a test light, check to see if there is power to the motor as indicated.

Here are a few links you may find helpful:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

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

Before you actually disconnect the wiring from the motor, inspect it to make sure it is tight. Also, when it is off check for corrosion in the plug.

Let me know what you find or if you have other questions.

Take care,
Joe