I have a shower that the water either comes out very hot or very cold. There isn't a happy medium (warm). What is strange is that if I turn the dial all the way to the left I hear a thump in the wall and then the hot water comes out. I turn the dial back to the right to get cold water to make the water warm, nothing happens until I hear another thump and then the water turns cold. I have also noticed that the cold water in the sink is more warm than cold. I'm not sure if that has any relevance. There are 2 showers in the house and only one of them has this issue. I've replaced the dial/handle thinking it was that, and that didn't make a difference.

Thanks,
Cesar

You were close, the dial is mounted on a mixing valve and the valve is the issue. If weknew which valve you had and how handy you are we might walk you through the repair or you could hire a plumber or handyman. I'd replace the valve