I tend to use my ac in the summer a lot and then in the cooler months when cooling isn't needed, I still let the compressor run a couple of times a week to keep things working ok. So today I ran the ac and thought I would set it to the coldest. I am not aware of any leaks or the like but it no longer gets cold at all. I have checked the relevant fuses and all seem ok. Normally when the ac is on, the noise from the engine bay is slightly higher, I presume from the 2nd fan kicking in and the clutch on the compressor being thrown. It no longer makes a louder noise, nor does the 2nd fan behind the grille kick in. This was a sudden failure, not a slow decline in ac efficiency. Any ideas what I can try next?