Air conditioner is charged but isnt blowing cold air

I have had tech check my Ac , It is fully charged and the pressures are were they are suppose to be but it is blowing warm air . The heater lines from the motor to the fire wall are extremely hot .We didn't know if there was a Valle that wasn't shutting off or if the controls are not switching to cold . I had the tech drain the system and charge to manufacture pressures and it worked great for a 7 days but then it started blowing warm air again . I took it back and the pressures were fine and the lines are cold as if to show cold is being delivered to the cabin , He did clean the condenser and we installed a new cabin filter . Please advise ?