Chevy & GMC Vans

Would anyone have any idea what would cause my atc fuse in my 2001 Safari AWD to keep blowing? This is my first winter with the van and I realized during it's first snowstorm that I only had 2wd. I found the 20amp atc fuse blown and replace it. It seemed to do the job but only for a few applications on snow after which it blew again. I have repeated this cycle about 5 times now and there is obviously something wrong.

Thanks for any feedback,
John

a short in the encoder motor?

Well I finally got around to replacing the encoder motor today. I had replaced the blown fuse and proceeded to do some mild holeshots on snow. To my disappointment the front wheels did not kick in as the rear were slipping and sliding. The fuse did not blow as it had done before with the old motor but I still have only 2 wheel drive. Real bummer as it seemed that I would momentarily have 4 wheel until the fuse blew prior to swapping the encoder. Any more suggestions out there?

Thanks, John

The only other parts are the prop shaft speed sensors and the control module.