Diagnosis
The adjustable window bracket isn't extended wide enough for your window opening, or the foam seals aren't compressed against the window frame.
How to Fix It
Maximize the bracket's width and use the foam strips.
- Fully loosen the locking knobs/screws on the bracket's sliding panels and extend them until they press firmly against the inside of your window frame.
- Retighten the knobs securely.
- Use the included self-adhesive foam weather stripping. Apply it to any gaps between the bracket panels and your window frame or sash.
If That Didn't Work
For horizontal sliding windows, the gap is often at the top. Cut a piece of rigid foam board or thick cardboard to fill the space above the bracket, and tape it in place from the inside.
Heads Up
Any unfilled gap defeats the purpose. The unit is trying to expel hot air out that hose; if it can just suck that same hot air back in through the gap, cooling efficiency drops to near zero.