My son has a 97 Chevy Z71 with a push button 4WD that clicks when trying to engage but will not. Changed fuses and they blow again. Any ideas?

Thanks in advanced

look for the short down stream of the fuse, some wire might have rubbed itself raw and the insulation is worn thru and the lead is touching the frame or the body, or, the sw itself is shorted, or the actuator is shorted.