I have a rheem raka-042-jaz a/c and the fan out side will not shut off on auto when the desired temp is reached. What would cause this?

The outside unit is the compressor unit and fan. Turn off the power to the inside unit which supplies power to the thermostat and compressor contactor. If the outside unit continues to run, the compressor contactor is fused or bound closed.

Next, I would remove compressor(cool) wire from the thermostat and if it shuts down, the thermostat is the culprit, If it doesn't shut down, you may have a control wiring short.