It can take an hour or longer for the unit to thaw depending on the extent of the freezing and whether the fan is able to run. Exchange the towels for dry ones if necessary. Turn off the air conditioner after it has thawed sufficiently for you to access the filter.Click to see full answer. Simply so, what causes a window AC unit to freeze up?The most common cause of window air conditioners icing up is a lack of adequate air flow. Room air is drawn over the evaporator coils where it is cooled and then re-circulated back into the room. Insufficient air flow over the evaporator coils will cause them to become too cold.Similarly, how do I defrost my air conditioner fast? To thaw out your AC, you need to take two easy steps. First, switch your thermostat to OFF and your fan to ON. This will start defrosting your A-Coil, found inside your home. Give your unit a few hours to fully defrost. Similarly one may ask, how do you know if your AC froze up? Look for visible ice on the outside of the air conditioning unit. If you see none, open the panel according to the manufacturer instructions and observe the cooling coils. The ice may be there. If you see no ice, the unit may still be frozen.Do you have to put Freon in window air conditioners?Air conditioners sometimes leak and need to have freon added to them. Window air conditioning units are used by many to cool apartments, homes, RVs and offices. However, units get old and can develop leaks. When this happens, the unit will need to be recharged by adding freon.