Sick of central air- what could it be?

-First our technician came a few months ago and added 8 pounds of freon and switched out a wire outside that had burned out. He also found a leak due to a cap missing from the last technicians from another company.A month ago he comes back because the unit would run outside but not come on inside. He said it was the mercury thermostat....After that he came back he discovered our relay switch was bad....Now, two weeks later after all of that work, the unit is not running cold again and its ice on the outside unit. What could it really be if he could not find a coil leak? I am so sick of central air now.find somebody who knows what they are doing, 8 lbs of freon in a residential unit means you were almost out and have a pretty good leak.... and ice on the outside unit means no air flow inside because of a dirty evaporator or a wide open TX valve... so could be a few things , so that's why you need somebody who knows what they are doingIs the AC unit's fan running? If the fan shorted out, that could cause the icing up problem and no cooling.