Hi Randy - Great Electrical Repair Question!
First off I'm assuming this 220 volt AC circuit is a 15 or 20 amp circuit. The 220 volt circuit for the AC unit most likely does not have a third wire dedicated as a neutral. Usually a 2-wire romex with a ground wire is run to the AC receptacle and the white wire is identified with black or red electrical tape designating that it is a hot wire. Because the ground wire is usually un insulated it can not be used for a current carrying conductor such as a neutral wire.
This circuit can be converted to 110 volt and a 110 receptacle can be installed during the winter months in place of the 220 volt receptacle, here's how:
To convert a 220 volt circuit to 110 volts - First the circuit must be positively identified back at the source panel. One of the power legs attached to the 220 volt circuit breaker, usually a white wire (as described above) needs to be disconnected from the breaker and attached to the neutral buss. It would be best to place a one-pole circuit breaker in place of the two-pole breaker, inserting a spare breaker or spacer in the remaining space, then be certain to label the circuit for it's intended use.
This is not the most convenient way to do this but it will work. The problem is that this procedure will need to be reversed in the summer time if you decide to use the air conditioned again. The idea of initially installing a dedicated 4-wire electrical circuit which could then be used as a combination of 1- 220 volt receptacle (for the AC in the Summer time) and 2-110 volt receptacles ( Heater in the Winter time) would be great. I actually do this when installing power for window AC units because I know sooner or later these units may require a dedicated neutral wire just like the electric dryers and the range circuits.
As mentioned above, if this circuit is larger than 20 amps there will be a few more items to address, so please let me know.