Hopefully you removed the cartridge before soldering.
Good day from Northern California
My wife and I have been long time DIY folk, 20+ years now. We are currently renovating our guest bahtroom down on the lower level of the house. It had rather ancient Speakman shower valve and my wife wanted to modernize the look a bit so we picked up a Moen shower set. I finished sweating in the shower and we turned up the water to the house. Yay for no leaks, except the valve doesn't seem to turn all the way off. It drips badly in the off position. Ideas on why a new valve would be doing this?
What Terry said for sure. You could remove the cartridge and flush the lines out/wash the cartridge off and try it again. If the cartridge is damaged you will need to replace the cartridge.
My bad.. I did forget to remove the cartridge. However I did pull the cartridge and happened to have another cartridge in a box in the garage. Replacing it did the trick. Thanks for the ideas guys. I love the website. With 2 more bathroom renovations on the horizon I am sure to be stopping in for ideas and assistance.