I have a 96 K2500 that had the same problem. The fuse kept blowing because the heating element was drawing too much power (was my guess). I bought a Dorman replacement actuator with the electric motor instead of the heating element. You also have to buy the corresponding wiring harness since the replacement actuator has two hots and one ground whereas the OEM had one hot and one ground.
Here's where I nearly went bat-crap crazy... The new wiring harness has an additional brown wire which is supposed to be spliced into an existing wire that goes to the transfer case switch. It is a nightmare to find the right spot to splice in. The instructions are very vague, and only because I found a diagram online was I able to find the correct wire. Even then, I could not splice in where it said to, so I spliced in elsewhere, and it worked.
Second, the connector from the OEM actuator was not the same as the connector on the replacement harness, so I had to ditch the new connector and splice in the OEM connector to the new harness. Problem was that the old connector had two black wires, and the new harness had a black and a blue wire, so I could only guess as to how to wire it up. Well, when you have a 50% chance of getting it wrong, there's a 100% chance you will get it wrong. So, it didn't work, but after I reversed the two wires, it did work. It's snowing today, so we'll see if it really works.
Looking back, I might have been able to tell how to wire it correctly if I had done some testing first, but I was not that smart.
The OEM heat activated actuators are total crap. Poor design, and prone to a very short life. Another disadvantage is slow action (or no action) when it's really cold outside, and when you shut off the engine, the actuator retracts and you're back in 2WD, like it or not. This is bad if you are counting on four locked wheels to hold your vehicle while your gone...
If you go this route, I would contact Dorman to make sure you are getting the correct actuator and harness. I found out after I purchased that there are several options, and that I just got lucky in getting the correct one.
