91 ford probe heater wont turn on?

I have a 91 ford probe and I can't get the heater fan to come on when I turn the knob.I tried to check the fuse but the only fuse I can find that would relate to the heater is the defog fuse but it's not like a regular fuse it's a black fuse you can full apart but I don't know how to tell if it's blown.Is there anything else I could try I don't have a diagram for the fuses under the hood to see if any of them would be the problem any tips will help thanks.