Vacuum or blow out filters. Dirt and dust cause a lot of air conditioner problems. Filters get dirty as well as the condenser; duct work also fills up with dust.
Tape over any holes in duct work with duct tape. Leaking duct work can cause the unit to run inefficiently.
Check the cables on the battery to see if they are corroded or if the battery is keeping charge. If this is the case, replace your battery. The voltage must be over 103.5. If it's not, the compressor, fan and even the thermostat may not function.
Check the fuses and replace if blown.
Visit a certified technician if the unit is leaking fluids. This can be a dangerous fix for anyone who does not know how to properly handle the fluids.
