Compressor is running in the outdoor unit. Even if the fan is running in the outdoor unit, the compressor may not be. Most compressor make a "compressor whine" when running, which is a low gutteral noise unlike the  air sound of just the fan.

  If the compressor is not running but the fan is, use your amprobe on your multimeter to determine the amps to the compressor. Turn off power to the unit. Use a 5/16" nutdriver to remove the screws on the coverplate to the electrical components of the air conditioner. Wrap your amprobe around one leg on the incoming 220 volt circuit. Return power to the unit. The reading on the multimeter should match one of three things: 1- The Running Load Amps (RLA) which would mean the compressor is working, 2- The Locked Rotor Amps (LRA) which would mean the compressor is locked up and needs replaced, or 3- A lower amp reading indicating the fan only is running. All three readings should be indicated on the rating plate of the outdoor unit.