4 Wheel Drive/SUVs: fuse blows when I shift to 4wd, transfer case, actuator

Question
Hi, I have a 94 3500 6.2 diesel. When I put it into 4wd the fuse blows. I installed a new actuator, still blows. I know I probably have a short but here is the mystery. I turn the key on and put it into 4wd, seems like it works and does not blow the fuse. As soon as I start the engine and shift into 4wd it blows. What would be the difference? I am  baffled.

Answer
Kevin,

with the engine off you have 12 volts going to everything. With the engine running you have 14 volts going to everything. I feel like you have a bad wire going to the transfer case or the front axle causing the problem or maybe a bad ground. Check all of the wiring and see if there is a pench or melted wire somewhere, this could be drawint too many amps from the fuse

Matt