[Trainer]

Chester,

Exercising the valve by turning the knob all the way one, then all the way the other way and back to where you started is recommended. I do not remember if I mentioned this in the seminar.

I have not heard of cleaning the valve.

[folivier]

That's the problem, how to get CLR or vinegar to sit inside the valve long enough to do some good cleaning. The valve is laying horizontally and there is hot water from the aqua hot.

[folivier]

Here are a couple pictures showing the valve inside the mixing valve body. Don't see anyway to remove it, looks like it's pressed in.
The thermostatic part presses down on this spring loaded valve to open it to allow cold water to flow in.

[arcticdude]

Why not use a funnel and some appropriately sized tubing shoved over the open end of the mixing valve? Fill it with vinegar, clr or etc and let it sit. As long as you haven't drained the entire system, it should only take a little extra to fill everything.

[Trainer]

Forest,

Depressurize the system. Close all water facutes. Remove valve body loosing about a cup of water.

Now both sides of the valve are full of water so if a seal can be made on the empty valve body, not much CLR or vinegar would be needed to flood valve body.