[jimcol]

To piggy back on to what Bill said tighten the screw at the breaker and the neutral in the breaker box. While you are in there might as well check all terminated wires, hots, neutral, and grounds. You won't be the first to find loose connections. After tightening all connections in the power distribution panel go to the other end where the power ties into the air conditioning unit and check the connections there. More than one on this form has found loose wires under the wire nut.