An air conditioning unit has a drain line that assists in removing moisture from the unit to the outside. It is a common issue to have a drain clogged, which is why it is important to regularly inspect, maintain, and clean your condensate line.
Indication of a clogged drain line can be signs of water leak near the air handler, the unit malfunctioning, or the unit shutting off.
If you have a shop vac on hand, you can unclog the drain by assessing the service opening on the drain line, and vacuuming out the line. If you're not too handy, call a trained-technician in order to resolve the drain issues.