I have posted at Gameboomers a number of times about this one.
First, you have to make sure the "Heat" is on, which is turned on by having the Bahro recognize the drawing of the Heat symbol on the slate. You'll know that it's running if the valves "pop-up" from their base, giving you a hot-spot to grab them. If they haven't popped-up, then the Heat is not running. Get the Heat running first.
Here is how I described the way to move the valves in another post:
"These valves are funny.
Yes, I found that if you try to click and drag at the top of the valve lever, it is hard to move it.
I clicked and dragged by grabbing the bottom of the round part of the valve, BUT it doesn't drag the way you'd expect. If you want to turn the valve lever to the LEFT, you grab the bottom and drag it LEFT (you would expect to have to drag it right, but it works opposite of what you expect).
Also, I had to click and drag it twice to get it all the way to the LEFT (i.e., the first drag brought it to center, then I releleased and dragged it a second time from center to LEFT)."
If the Heat runs out (it lasts about 90 seconds) just run it again by using the little "shortcut" icon that will appear on your slate after you get it the first time.
Let us know if you solve it!