A/C. Where is the fan controller located and how do you determine if it's operating properly or not?

I have what appears to be an operational a/c system. Yet it doesn't operate. I have proper readings on the low and high sides, full of freon, the a/c button on the dash lights up when depressed. But no clicking sound at the compressor. I've heard on these cars that the fan controller can cause these systems to malfunction if it's not working properly. I've also been referred to replacing the compressor clutch. I would like to do a proper diagnostic before assuming that the clutch is bad. My mechanic is anxious to replace the compressor/clutch asap. Short of work these last couple of weeks. Needs to play "catch-up" with my money.

thanks again guys