I have a 09 rx 350 and the ac light is on and has freon but ac clutch not engaging. Is the ac amplifier the problem? does this car have a ac relay?

 

IIRC from a year ago, there is no A/C Relay, but there is an AC Amplifier by the glove box. I would start by having it scanned and note all DTCs, check fuses. How many miles on car? Clutches can go bad or lose connection.

 

How did you determine that the a/c system has refrigerant (freon)? If the refrigerant level is low, the compressor will not run because of a pressure switch. On some cars (I don't know if this applies top Toyota) the compressor will not run if the refrigerant pressure is too high.

Besides the items mentioned by Mesquite77, there are a couple of other sensors that could fail and cause your problem. Such as the a/c thermistor, the a/c room temperature sensor, the a/c ambient temperature sensor, among other things.

My advice is to take it to an air conditioning shop.