Air Conditioning - fan stops running

The fan on my AC unit has stopped running recently. It is very sporadic. Sometimes it will not start when the thermostat is first triggered and the AC does not blow any cold air from the start. Other times the fan will start after the condenser makes some grunting noises and the AC is cold but after a 10 minutes or so the fan stops running and then the condenser will stop. And sometimes it starts up and runs cold until the desired temperature is met. My unit is 21 years old but I had an AC guy out and he said that the unit is still in good shape but I need a "hard start" kit. I would believe this but for the times when the unit starts but the fan stops running before the desired temp is met. Do I have a fan motor going out or do I need a "hard start" kit? The AC guy did not think it was the capacitor. He measured a constant 30.0 coming from the cap. I am very puzzled so any advice would be greatly appreciated.

Thanks,
Brad

Is this the in door fan does it come on at fan on ok? Or is this the out door fan on the condenser unit????
You said its 21 years old, 15 is about the life of a AC unit. I dont think you should spend money on this unit. Id get a new one with a higher SEER on it and save money in the long run.

ED ;)

It's the outside fan. And now the outside fan will not come on at all. I agree that I should probably replace the unit but I'm going to replace both capacitors and see if that gets it running again. For less than $20 it's worth it if that fixes it. If it's the fan motor or the compressor then I will just replace the whole thing.