Loss of water presure

Possable there is some rubber in it . But it could be blocked with scale fApart from the hot water the valve out to clean it not much more i can say .I would look on u tube and see if it shows how to unblock the valve .

Is the hot water pressure good at other fixtures in the house? I'm guessing your newer valves have a scolding adjustment that is set very low. Check the instructions that came with the valve assembly.

Possible issue with pressure balancing cartidge, When you remove parts, turn off water, remove parts, slowly turn on water and see if brass valves lets water out. If yes pressure balancing cartridge or cartridge itself is defevtive.

just turn the water valve down some

I think you are on the right track. The first thing I would do is change the cartridge. While you have the valve apart examine the inlet ports as good as you can to see if there is any mineral buildup. You can use a short length of a small gauge mallable wire to run into water ports to se if you can break anything loose. Another thing you can do is to turn supply stop on slightly while you have the valve disassembled to wash any particles out. Hope this helps you and thanks.

It is due to the water pressure. You may need to install
a pressure relief valve at your main cold water line, so
you can set the water pressure and prevent your valve from vibrating, that is it it is annoying you,.Otherwise,
just let it be..

are the handle extensions on the cartridges all the way. i know sometimes the moens are a pain after you put the trim on to get them on and seated right so it actually spins the cartridge. also check the cartridge alignment the cartridges have little white tabs on the sides that correspond with a slot in the valve body if they aren't aligned it won't shut off either

you need to change the cartridge

ever since the pressure balancing regulations came out for shower valves, they have went from simple to very complicated devices. sounds as if some foreign material caused the valve to stop working. that valve is quit difficult to reassemble correctly because there is only one way it works and can be assemmbled many ways that do not work concerning alignment of the ports. if you dissassemble it and check that all the moving parts are functioning in the balancing cartridge you can then look closely at the alignment of the ports on the cartridge that the handle is connected to. understanding how the port align as the handle is turned should assist you in assembling it correctly......hope this helps.

The Moen Posi-Temp Valve is a pressure balanced valve and when not used for long periods of time they can stick causing only cold or hot water to pass through the valve.
A New Posi-temp cartridges can be purchased at most plumbing supply houses or big box outlets such as Lowes or Home Depot.
As long as you had cold water before, a new cartridge will solve the problem. In the future it would be wise to occassionally operate the valve at least a couple of times a month in order to keep the pressure assembly from becoming lodged in position. Just follow the instructions included with the new cartridge on the proper removal of the old cartridge and the installation of the new cartridge. a little silicone grease inside of the valve before installing the new cartridge will also help.
Be sure that there is no particles of the old cartridge left in the valve.
sanray