My dog Rufus is a male Chihuahua/Terrier mix. He is around 6 months old now and we have not been able to house break him yet, and seem to be making no progress either. The only way we've been able to avoid accidents is to take him out constantly (at least every 45 min), and even then it seems to be hit and miss. A lot of times I will stand outside with him for 10 or 15 min, telling him to go repeatedly to make sure he's done, and when we get inside I turn around for 30 sec and he's gone on the carpet. it is cold outside, but i'd think that he would get the picture that he can come inside when he does his business, instead of standing around for 15 min. i praise him every time he goes outside like he's supposed to. Also, he's a very quiet dog, and will not make any effort to let us know when he has to go. Any suggestions?
Try crate training him. Keep him in a kennel unless you are taking him out to use the bathroom. After he goes outside praise him and possibly gve him a treat. Then when you bring him back in play with him for a few minutes than put him back in the kennel. Everytime he goes outside you can extend the time he gets to play. If he goes in the house again start back at square one.
I would try crating him between potty breaks. If you're taking him out every 45 minutes, he's getting no bladder training. He has to learn to hold it for a period of time. Give him 30 minutes of play after going potty and then a couple of hours in the crate til the next break. And get some Natures Miracle and a blacklight and get rid of the urine to prevent resoiling.
The only thing else I could suggest is to make sure there is no physical reason for the problems you are having. Have a vet make sure there is not bladder infection. Other than that, a very strict routine and a crate should do the trick.