How do I potty train an older Yorkie on puppy pads?

I adopted a 1.5 year old yorkie and was under the impression that she was housebroken. I soon found out that she was not, so I have been trying to train her to go on the puppy pee pads. I am keeping them in the same location so she knows where they are all the time. In the morning she will go on them, but in the afternoon she doesn't want to. I have her crated when I can't watch her, but she doesn't seem to mind going in the crate so crate training has not been working either. This has been going on for about a month, and at this point I'm wondering if she's just too old and stubborn to train? My other dog took three days to potty train, but he would not go in his crate so it was much easier. He has since passed away so he is no longer around. She also goes crazy when she's crated and barks and thrashes around. Help!!!!