I don't think you have enough proof that the ECC is the culprit to justify replacing it. I don't think it is very common for the ECC to fail. What do you mean the A/C totally shuts down? Is the compressor turning (watch near the compressor clutch)? Does the fan blower turn off by itself? What is the refrigerant pressure when it is running, when it is off? Will it come on if you short out the low pressure switch in the line near the firewall? (remove the connector, put a paperclip in between the contacts, don't let the clip touch anything else, like metal). When was the system "professionally charged", and WHY did it require charging? Did you have poor performance before? Did the problem arise soon after the PRO worked on it? The ECC fault lights will NOT show a fault for improper refrigerant level. My theory is your PRO improperly charged your system. Or sabotaged it. But I'm a pessimist and don't trust people with my vehicles. Perhaps you have a massive refrigerant leak.