My Carrier central air conditioner is 8 years old and it is not cooling. The vent blows air but the fan on the outside unit is not working. Any suggestions on how to fix it?

Check capacitor to fan... turn power off to condenser... pull electrical panel off condenser... should be a silver round or ovel can looking thing with wires going into the top side of it... this is a capacitor... if it looks swollen like you stuck a can soda in the freezer... its bad and needs to be replaced... if not than more than likely the fan motor itself is bad... some hardware stores such as ACE Hardware carry condenser fan motors... check fan motor horse power such as 1/4 HP or 1/2 HP

Did you check to make sure breaker to outside unit is OK,,
If you end up replacing the motor tag where the wire go and take the old motor with you when shopping for a motor,, it has to turn in same direction, have very close to the same rpm`s as well as same horsepower

If the fan and or the compressor is not working check for tripped breakers,bad run capacitor or bad contactor.