When working correctly, a window air conditioner removes moisture from the room air; that moisture collects on the evaporator coils inside. How much water collects, depends on how humid the air is. So, even when everything is working perfectly as designed, the air conditioner will drip some water from the rear outside but none from the inside.
If your air conditioner leaks water inside the room, here are some of the most common causes.
The coils inside the air conditioner can form ice if the air filter is clogged with dirt. Remove the front grill to inspect the filter. If the filter is dirty, wash the filter with water and let it dry before reinstalling it. If the coils continue to ice over, contact a service provider.
The air conditioner should be tilted back slightly so water drains outside. Check that the air conditioner is level from left to right and tipped slightly from front to rear.
The rear of the air conditioner has a drain hole or notch to allow excess water to escape. Debris can clog this opening, preventing water from draining out. Use a wooden stick or skewer to unplug the opening—don’t use a metal pick or screwdriver, which could puncture the coils and cause major damage to the air conditioner. Also, don’t drill holes in the bottom of the cabinet.
Blocked drain path
Small channels allow water to drain from the front of the air conditioner to the rear. When these channels are blocked, water collects in the front of the cabinet and can’t drain to the rear.
Pull off the front grill and remove the filter. If you see a pool of water under the coil but little or no water in the back, these channels could be blocked. Remove the air conditioner from the window and use a low-pressure water hose to flush out these channels and the drip pan.