Sorry if I am not using professional terms. I am just starting to learn about HVAC, by learning about my home unit first. The unit outside of my home has ice on it. I have 2 friends who have received their license but giving me different answers. 1 said that it is due to low freon. There might be a leak somewhere. So, I told my cousin to come and fill the freon, but he said that freon cannot be measured when the temperature is cold outside. I live in Charleston, SC and the weather is around 50-65 degress. Is that true? Please help!!