Basic Problems
Before fearing the worst, check the temperature the unit is set at. If this number is higher than the actual ambient temperature of the room, the air conditioner will not blow cool air. Also, make sure the air conditioner is not mounted in a place where it receives direct sunlight because that can heat the unit.
Dirty Unit
An unclean unit can lead to a lack of cool air. Check the condenser coil on the outside of your unit for dust and debris. If it is clogged, it will not function properly. Use the brush attachment on a vacuum to clean it.
Calling for Help
If you have checked the temperatures and cleaned out the filter and condenser coil, it is likely your air conditioner will need servicing. Contact your local Sears to speak to a technician.