Heater fan not working correctly?

The blower resistor is on the bottom of the blower-Check all the HVAC fuses, HVAC relay,High speed blower relay and blower switch- Here is the blower motor, compressor and HVAC wiring below so you can see how the system works. This guide will help us as well

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

Check out the diagrams (Below). Please run this test and get back to us.

You will find a melted terminal and possible connector body at the blower resistor. A poor connection creates resistance, and resistance creates heat. Ideally, you will either need to obtain a harness with leads, or a terminal and connector body to perform a wire repair. More than likely, you will need the resistor also.

When you turn the AC/heater on does anything happen? Do you have any air flow? If not then yes, it could be the blower motor. We need to test for voltage at the motor and see if you have voltage when the switch is on.

I attached the test for the blower motor but again, I think the first thing is to just check for voltage because if it is there then the motor is most likely failed.

Check to see if resistor is getting power from switch just probe any the wires as you move the switch. Then probe blower to se eif it's getting power if not it's probably the resistor pic included.

You'll have to remove some panels to get tot eh resistor on passenger side they will either have push pins or small screws holding them in place.

Pull the connection at the resistor, if you can get it apart. Often times a poor connection results in a thermal failure. Replace the resistor and connector. It is available as a harness, makes it easier.

Pull the connector from the blower resistor, under the rh dash, near the blower motor. It is a red connector body, 5 or 6 pin configuration. Check the power supply terminal, you will probably notice the heat damage to be obvious. Replace the terminal and resistor, it is usually caused by high resistance from the poor connection. You will need another terminal body as well. I don't know for sure if a harness connector with leads is available, then you would just splice it in with provided crimp and seal butt connectors.

Pull the connection at the resistor. If it is burned, replace the resistor and conenctor/terminal. There is also a harness available with that connector, it is a bit more in price, but is plug and play.

Power the brown wire at the blower motor from the battery and see if it comes on if so do below

Check and test the HVAC relay, High speed blower motor relay, blower motor resistor, BCM and HVAC control module-This one can be tough to deal with best bring it in.

For jbl0509, check the connector at the blower resistor. Poor conection usually causes a thermal failure, you will see the signs when you get it disconnected. The resistor, and terminal will need replaced. Optionally, there is a harness available through GM that includes that connector.

For perkusmc2171, is there air coming from other than the dash vents, like the floor or defrost vents?

Check the red connector body down at the resistor for signs of overheat. You will need to replace the connector body, resistor and terminal. You can also get a harness for that circuit that is not too expensive. It is just plug and play, after you remove the glove box and such to access all the connections.