Heater blow cold air

Hello,

It sounds like the blend door actuator on the passenger side has failed.
The blend door actuator controls the hot and cold air flow.
Over time with normal use the actuator will fail. Many times when the actuator fails it will get stuck on one position (hot or cold).
The blend door actuator is located on the passenger side behind the dash panel in the HVAC box.

Here is a helpful article:

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

I have attached diagrams for your reference.

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