1997 nissan pickup ac

My AC blows cold for a little while, then it blows warm. If I wait and turn it back on the cycle repeats it self. I had the freon filled. Please help not sure what to do?

Is this vehicle sitting still when it blows warm? If it does it while driving it could be the evaporator is freezing up. This could be from too much dirt and dust collecting on the evaporator in the dash reducing airflow. I am not sure how to clean it in a vehicle, I have only seen it on home window AC units.

If it does it while stopped, the fan clutch is bad most likely

Sounds like you are icing over. This means the freon you added is leaking out. You will need to find the source of the leak. One strong possibility is the schrader valve the freon is added through. After 15 years, you upset them when you opened them to add freon and they probably didn’t reseal completely.

Thanks guys I will tell my local mechanic.