A/C compressor won't engage

That pretty much sums it up. When the A/C is switched on, the compressor doesn't engage or make any type of noise like it's trying. Just dead. I'm guessing it's a switch/sensor or something, but I'm not sure what to test. Bentley manual shows me where everything is, but no real clues on diagnosising this particular problem. Anyone have some ideas?

common problem when it is not engaging is that it does not have enough refrigirant (r134a) in the system.

I would check the obvious things first, such as all fuses shown associated with that A/C system. I would then check to see if the fans come on when you engage the A/C button as the compressor will not engage without this. If the fans are not running you could have a fan or fan control module problem. After this I would check for wiring problems, as I found my ground from the A/C compressor was broken at one of the connectors between the compressor and the grounding point. I would also verify if 12V shows at the compressor connector when the A/C button is engaged or not. If no 12V and wiring is good you will need to start checking sensors such as coolant temperature, ambient temperature and the A/C pressure switch. If 12V is present you probably have a clutch failure and will need to replace it.

do the fans come on? Check the fan fuse on top of the battery.

The fans aren't coming on either. Do the fans kick on immediately with the compressor? I checked all the connections but haven't pulled them apart to test them yet. Will check fuses and such first. I recently replaced the radiator but I'm not sure if the A/C was out before that or not. It wasn't hot enough to run it. When I tried to use the A/C recently (after swapping the radiator) it was zonked. Thanks.

Both the fans and the compressor are controlled by the fan control module which engages them on direction. As noted earlier if the fans don't come on it could be fuses, wiring, bad fans, bad control module, bad sensors or sensors detect an actual problem that leads to the module correctly refusing to engage the system.