Moen 1222B shower water mixer cartridge - warm water on low flow

[aaltor]

When I turn on the shower lever just a little bit (water dripping), the water is warm. When I turn it on more, the water turns cold (like it should).
So when the water flow is very low, it is warm.
It used to be OK before I replaced 1222B cartridge.
I thought it was the cartridge issue, so I replaced it again, but the issue remained.
Does anyone know why it might be happening?
Thank you!

 

[Mr_David]

proper operation of a Moen Positemp.

Off. the handle is pointing down at 6:00 o'clock.
turn on counterclockwise and you get cold
as you turn more it should get warm then hot.
The handle should stop at about 10 o'clock.

the cartridge has a H/C on the front and should be on the top where you slide the retaining clip in.
Look at the valve inside the wall
On top of the barrel, that he cartridge is installed into, there should be the word "UP". If it's on the bottom then the valve is installed upside down.

pull the core and make sure the ports inside the barrel are clear.
Sometimes removing the old core the black neoprene seal tears and a small piece may have got left inside.