Compressor cycles on and off

Stick a temp probe in the center duct. Start the AC and set to MAX AC with fan on HIGH, pay attention to how long (time wise) it takes to start cycling and watch the temp reading as the comp cycles on and off. Set AC to NORMAL and see if the cycle time extends. Make sure the drain tube is dumping water, if its plugged water will accumulate and freeze on the evaporator. As it freezes the airflow will decrease and freeze up even more. You also may have a dirty evaporator, full of old leaves, dirt, etc. restricting airflow.