We have a Carrier AC unit that is about 9 years old. If the unit has been off for a while and we turn it on it runs fine-both the fan and the outside unit. It cools the house and everything seems fine. Then at some point the outside unit stops while the fan inside is still blowing. I'll turn it off and back on and still nothing. We called someone out and he said we were low on freon and that when that gets too low the unit will kick off. So, we had the freon added and it came on cooled the house down and all felt good until it kicked off and then wouldn't come back on again. I don't think it's the thermastat because that seems to be working fine and correctly for the heater so far. Any ideas?

It could be that the compressor motor is going bad and overheating. It has a thermal overload that shuts it off if it overheats. Once it cools off, the motor has power again. The over load could be bad too, shutting off too soon. They are a little round thing in the motor with 2 wires going to them. Hard to get at, and hard to find replacements.

your system have a major leak... was the leak repaire before the freon is added...

The guy didn't mention anything about a leak. How or where do I look for the freon to see if it's still in there from when he recently filled it?

The older automotive systems had a sight glass, but I never noticed one on either my current home system, or the old one. If it did have one, it would be near where the tubing goes into the compressor on one or the other. Look for a pipe fitting looking thing with a clear glass center. You should be able to see the liquid level in it. Usually it is checked using pressure gages. I don't know what the pressure should be, and an ordinary tire gage doesn't fit the special Freon pressure fittings.

Where do you live that you still are using the air? In the United States it is illegal as well as costly to add Freon without checking for leaks and repairing them. If you have a very small leak, the system could be low, but the guy might not be able to find it. A small leak shouldn't have caused the Freon to be low again so soon.

I still think the problem is the compressor. It may have been damaged by running too much due to the low Freon.

If the fan outside doesn't come on, it could be a wiring problem. The 2 smaller wires to the compressor unit should have 24 volts AC to them. You should be able to hear a clicking outside while somebody inside turns the thermostat on and off. If not, the relay could be bad. When the thermostat send 24 volts to the little wires, they energized the relay connecting the power supply to the compressor and fan.

If you don't know much about a/c equipment you shouldn't do anything to it, you should call a company that knows what they are doing!

In some models they did not put a start capacitor on them and as they age they become harder to start like labman told you. There is a thing you can have installed on your condensing unit that will give it the boost to start it... they are not very expensive and it may give you a few more years.

I am not sure this is the fix but just a thought to add to the other suggestions