My transfer case fuse keeps on blowing cant find out why 1999 gmc suburban

Check the four wheel drive actuator on the front axel. It's on the front right side of the front differential housing. It's round with a big hex on it where you would put a wrench, I think it's 1-1/4". Anyway, follow the wires there's a plug about 6 inches away, unhook the wires going to the actuator. Now see if it still blows the fuse, if the fuse don't blow the actuator is the problem. It just scerws out and the new one screws in and hook up the wires. This is a fairly common problem with those trucks. On the early K series GM had the four wheel drive and the heater fan on the same circuit. The actuator would go bad and blow the fuse so now your stuck in the snow with no heat. I think GM changed that in the later years.