I noticed that the copper tube was cold, and had a little frost on it the other day, but everything was running fine until I changed the motor on my other ac unit because the fan wasn't turning on it. Any suggestions? I read that if I turned the fan to the "on" setting, if there was a freeze somewhere it would defrost it and it should run fine. HELP!! Im in Vegas and its getting HOTT!

Is the motor running, or are you just feeling for air flow? Coils can take a long time to defrost. Air conditioners freeze up for a reason. Probably low on refrigerant charge, or airflow problems including bad motors, PC boards and plugged filters or coil.