The lid of the fuse box that lifts up is on top of the cover for the entire fusebox assembly. I believe there are 6 screws total. When I test the AC I put it on the coldest temperature (min), put the blower on max, push the recirculating air button and let it run. If the AC has a full charge, the compressor and the auxiliary fan will cycle on and off. I often find the fuse in the relay blown, it is GM style 10 or 15 amp.