My 740 ac has been sitting for 3 months, but has been used once every other week. When the first hot day arrived, I turned on the AC and it made the usual sound was on for 5 seconds, then shutoff, turned on again for a few seconds and then off. Keeps happening continously without ever staying on - thus the the ac never gets cold.

When I checked under the hood, the compressor wheel turns then stops, turns and stops.

Any ideas.. Thanks.