AC diagnosis?

I have a 2002, installed a turbo within the last few thousand miles. I noticed today that the AC isn't working. The AC switch lights up, but there is no compressor load on the engine (can tell by no change in idle note) and, of course, no cooling. I'll check over any underhood electrical connectors I can find, but beyond that I don't know where to start. I assume that a refrigerant leak would cause a "no pressure" situation and would electrically disable the compressor, but I don't know that for a fact. Also, AC has worked fine until now, not overpoweringly cold, but sufficient for TX.

Any tips?

EAsy way to check compressor function is to jumper the low pressure switch. Only do it briefly, but it should kick-on the compressor if there is nothing else wrong with it. That would be a dead giveaway for a refrigerant leak.