Why doesn't passenger side put out warm air from all vents anymore?

Hello, First, check your fuses. The blend doors have a fuse, but normally they are in conjunction with other things that you would have noticed failed. Blend doors are inside the HVAC ducts, and they change the type of air (hot or cool) that you receive through the vents. Since you have only once side doing this, you have at least dual zone climate control, so each side has its own blend door. The passenger blend door is turned by an electronic actuator (a little motor), and when this goes bad, your symptoms are replicated. Fuses first, as replacement of the blend door actuator might actually be a sizable job.