4x4 out, blows #24 fuse

My 1996 Yukon's 4 wheel drive has been working throughout the winter season, but now the 4 high and low will not engage. The engaging buttons on my dash continue to blink, and not engage. I checked the fuses, and my 25 amp, #24 fuse was blown. I replaced it and it went out again immediately. Will replacing the actuator fix this, or can this be caused by a short elswhere in the system? Any help is appreciated. Thanks