First off, you're not the best person to be searching for a refrigerant leak - which, by the way, may or may not be freon depending on the age of your AC compressor. Rather than check for actual leakage, check for performance. Here's how: Measure the temperature of the air inside the house at a return duct, then measure it at a supply duct nearest to the air handler. If the system is performing normally, you should read a 12 - 20 degree differential. If the differential is less than twelve, you're well within your right to demand repair. As far as your home warranty company's refusal to address this problem, this is unfortunately somewhat typical, and I can only suggest you be very persistant with them, and always ask to discuss the matter with a supervisor. Good luck!