The latest in a continuing series of annoyances from our American Standard kitchen faucet: it became increasingly hard to turn it on with the handle all the way to the left in the “hot” position. Bear in mind this valve is less than a year old and I replaced its predecessor two years before that, after maybe a decade of service from the OEM valve.
Pulling it apart revealed the problem, which requires a close inspection.
The view from the “cold” side:
And from the “hot” side:
The valve handle stem pivots on the 4 mm shaft passing through the black “engineering plastic” shape inside the red hot-limit ring. This top view shows the overall layout:
The shaft has worked its way leftward, toward the “hot” side, until it bumped into the limit ring. The right end of the shaft hasn’t come completely out of the inside of its pivot, but it’s apparently gone far enough to stop pivoting freely.
This may also explain how the previous hot-limit ring worked loose: the misplaced shaft applies torque to the limit ring as we move the lever to the “cold” side. I don’t know how the ring worked its way upward from its positioning notches. Overall, it seem plausible.
Installing a new valve isn’t going to get us a better design, so I must figure out how to keep the shaft in the middle of its travel. Perhaps replacing it with a slightly longer shaft will work around the problem, because it simply can’t slide in either direction.
Loosening the three screws holding the cartridge down (and applying pressure against the seals) reduces the force required to move the faucet, even with the shaft in the wrong position. This suggests the valve body distorts slightly, so I loosened all three and (roughly) equalized their torque; the valve isn’t leaking and we’ll see what happens next.