As far as the not defrosting in certain areas-that indicates that one of those defrost elements (lines going across the glass) has a break in it. Difficult to repair. Only way I know of is a kit from someplace like Eastwood or similar, that allows you to make a small patch over the break. Sometimes you have to look with a magnifier to find the break. As far as the defroster relay, I believe it should be in the passenger (right) side kick panel area, or possibly under the passenger seat, but I'm guessing here.