leak in ac line on 1999 Ford F-250 Super Duty

I know that I need to add ac coolant but I think there is a
leak somewhere because it doesn't get any cooler inside the cab.

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1 answer
Add the freon and run the system for a minute, shut off your engine and see if you can hear a hissing sound, which will be where the leak is. You may have to have a shop do an A/C dye test, but sometimes I find the leak with a careful inspection after I add some freon.