If your air conditioner is saying FL, it can be a concerning indicator that something might be wrong. FL stands for float switch, which is an important part of the AC system. This switch will detect when there’s too much water in the drain pan and shut off the system to prevent damage. The most common cause of this issue is a clogged condensate line or pan, which prevents water from draining properly and lets it build up until the float switch trips. Other possible causes include a malfunctioning blower motor or fan belt, defective indoor coil, bad control board, blocked evaporator coil fins, low refrigerant levels or incorrect airflow settings on your thermostat. To resolve this issue you should contact an HVAC professional who can assess what's causing the problem and make any necessary repairs so you can get back to enjoying cool air in your home again!