I have a vintage 1971 Price-Pfister single handle shower-tub mixer valve that has decided not to shut off without a lot of handle wiggling. I took the cover off, and for the life of me can't figure out how it works. The body is cast bronze, and the only apparent working part is a little nylon spinner about 1/2" across with a gear on it.
Are valves like this even repairable? I can't see that there is anything wrong with it. It is sweat-connected to 1/2" copper pipe, so it would be fairly simple to cut the pipe and solder a new valve into place. It's installed in a tile wall, but with the trim removed there is just enough room to reach the plumbing. I just don't want to buy a new valve if I don't have to.
Any tips on this little piece of archaeology? There is another one just like it in the other bathroom that is still working, but acting kind of feeble. That one seems to not turn full on or mix full hot.