2001 a/c problem

I have to go work on my sisters a/c in the morning and I have talked to her and she said when she hits the a/c button on the dah it does not even light up. I had her check the fuses and she only found a 7.5 fuse and it is not blown is there another fuse somewere. I normally have to put a can in every summer. But I am not sure what I am in for this time since the light is not even on. I also think the cycle switch is like a 4 prong not a standard 2 prong so not real sure what two to jump to make it turn the compressor on to check freon level. Any help or ideas before I head there in the morning to make sure I bring everything I need 50 miles away from me. Thanks in advance.