The driver side wiper stop working.

I went out to my truck on my break, it had snowed so, I started the truck and cleaned it off and it worked just fine. But, when I came out to leave it work not work. I thought that maybe it had just frozen up and it would be alright in the morning. It worked this after noon for a couple of swipes and then it stopped. The passager side worked last night and this after noon just fine. I would pull the driver side blade up and put it back down and it would work for a couple of swipes and stop again. Every thing seems to be connected and solid. What could be the problem?