So..... it worked fine and was blowing cold one day, then started blowing cold the next?
First thoughts fan belt shredded off, verify it is installed and tight. Loss of refigerant (leak in system) Possible fan clutch issue. Make sure the fan is not freewheeling when you spin it. Are you experiencing any overheat issues. Check condensor for debris on the face of it. Clean the cabin air filter/screen. Run the truck at 1500 rpm with the ac on high and windows down. Look at the compressor. Is it locked in??