Step 7: Voila! You're done.
If everything went as planned, your car's air conditioning should be ice cold! Enjoy.
If not, let's try to figure out where things went wrong:
The needle isn't moving/I don't think any refrigerant is going into the system.
Be patient. It takes a fair amount of refrigerant to raise the pressure. If you still have issues, check to be sure that you connected the dispenser to the fill port properly.
Help! I think I put in too much refrigerant.
Double check that the condenser hasn't disengaged. The pressure can spike quite a bit when the condenser disengages. If the pressure is still too high, I cannot recommend that you attach the dispenser to the fill port without a can and squeeze the trigger to release the excess refrigerant, because that is illegal. You must take your vehicle to a mechanic.
The compressor won't engage!
If your compressor will not engage, add half a can of freon. If it still will not turn, it is likely broken. Do not add more refrigerant! You will need a mechanic to repair this problem.