Air conditioner

Advise from previous tech that I was over charging the system because I had put two cans in one yesterday and one today. I check it with the hoses before I put the 134 in and hoses were showing low and when the tech told me I had put to much in I had some removed and the gauge is between 45-50 which is what the hose package says it should be but it is still not cooling. The metal pipes where freezing before I put first can in apparently is not now but it is still not cool, it also makes a grinding noise when first cranked up and seems to be coming from compressor, compressor is runningwhere to next?