Clicking from under the dash, but in the fuse box, when number 14 fuse is pulled, the clicking stops

My truck wont start and with the key off there is a clicking from under the dash, but in the fuse box, when number 14 fuse is pulled, the clicking stops, what does this mean, what is this fuse for? We have changed the battery and had the altenator checked to find it is bad. All we want to do at this point is get the truck started to get my son home. Its going to be cold outside. Before he pulled the fuse, he could step on the brake pedal and the clicking would stop. Does anyone have any answers for us