No heat or defrost

Hello, I'm Danny.

It sounds like you're having a problem with the blend door/mode valve actuator.It's an electrical motor that opens/closes an air door to direct air flow throughout the duct work/vents.Here is a tutorial showing what's involved to remove/replace:

https://www.2carpros.com/articles/replace-blend-door-motor

I've attached a picture below showing its location in the HVAC box located under the dash board.Hope this helps and thanks for using 2CarPros.

Danny-