So I drive a 90s ex cab and was wondering why or what component I need to replace. So the problem is that my AC only gets cold at night or on the freeway.

 

You need to replace the AC......general question with no info=general answer with no info.

you need to take it somewhere that can diagnose AC problems. Most likely it's just low on charge in which case you need to find out where it's leaking from or you'll just keep dumping refrigerant in to replace what you leaked. could also be blockages, bad expansion valve, bad compressor, etc with enough refrigerant.

 

If it works at freeway speeds when its got some airflow, but not at idle/low speeds, its the mechanical fan clutch.