When you recharge the system get a can of 134a that has the leak checker dye in it. It works pretty good and I was able to find the leak I had using it.
yeah,definitly use dye and refill the system.i usually tell the customer to come back when it's not cooling and i'll check it.dye is way more accurate than any sniffer device.
You dont need to re charge it unless the leak is very small,but you said you lost the freon in a month.Look at the consensor for oil trailing down,should look like a dark patches,and check at where the lines couple together,the fords are notorious for the o rings going bad,also check the schrader valves(where its charged).If you cant find anything on those parts,then it will need to have about a pound put in and use a freon detector.I used to replace mainly o rings and condensors and once in a while a evaporator.