I left my house unattended for a number of months. Before leaving, I turned off the water to the house and drained the lines. This was during the winter. Anyway, now that I am home, I notice my downstairs (basement) shower does not get hot enough. It gets warm but at its most hot, it is not as hot as it use to be. The rest of the house is fine. The other shower, sinks, etc. all heat up. I took photos of the parts as well as the pipes. Can anyone give any suggestions on how to fix this? I am not sure if this unit has a scald preventor on it. I tried adjusting the inner white collar but that does not seem to help. Or do I need to adjust the screws in the photo of the valve? Any suggestions would be great.
If you are experiencing low volume from hot water in this valve and have not changed any of the mixing settings from when it worked properly I would suspect a partial blockage in the hot water supply line.
Carefully remove the cartridge from the valve body and look for debris. While cartridge is removed turn the water supply on a bit to flush out possible debris. Reassemble and test for normal operation. Good news your valve body has shut off screws for hot and cold water on it!
A valve repair video that shows a very similar type valve is found here