Ac no working. Compressor not kicking in. Fuse ok. How do I check the relay?

if its low on freon,the pressure switch keeps it from turning on.find the a/c relay,and you probably have more in there with same part number,just swap 2 of them.most of the time it is low on freon or the pressure switch is bad.you can unplug the low pressure co switch,and jump accross the 2 terminals,if compressor comes on,its low on freon.do this with car running and a/c on.Carefully,be safe.