I visited a home where the AC was running constantly but not cooling effectively, and the owner noticed ice on the copper lines. This pointed to a low refrigerant charge. The problem was a slow leak that I pinpointed at a faulty service valve core using my electronic leak detector. I solved the issue by replacing the valve core, performing a vacuum to remove any moisture, and then recharging the system with the correct amount of refrigerant. This stopped the leak and restored the system's powerful cooling ability.