94 Lumina APV blows Ignition fuse
 

I have a 94 Lumina Van 3.1 litre that blows the Ignition fuse in fuse panelwhen I plug in A/C relay underhood. I switched relays with radiator fan (same Relay) and still blows fuse. I unpluged compressor clutch and low pressure switch and still blows fuse. Engine will run when fuse blows but kills charging system and heat a/c controls. I have limited wiring diagrams in manual but hoping someone can point me in right direction.