Ac not working, hot air only. When ac button pressed it blinks on and off when max ac dial activated

What is your question?

Continuous humming/whisle sound when ac button pressed and max ac dial turned towards msx ac.

What makes this problem better or worse?

Engine has been running for an hour, ac eas working fine up to an hour before problem

How long has your 2010 Toyota Tacoma had this problem?

Just started today, ac was fine before this, very cold