I have three thermostats, two of which do not work, and the third moves very little (< 0.5 inch). I am coming to the conclusion that it is the internal air expansion that makes the bellows expand and contract - can sombody confirm this? Somebody said there is an internal spring, but I do not think that is the case? If my assumption is right, than if I ID the holes in the bellows and repair them they should work again - right? Just wondering if they are originally filled with some form of inert gas or gas that has some special expansion properties? Anybody know for sure??

it was filled with oxygen pressurized to some pressure or partial vaccuum....

AFAIK it's just air...

starts out at (x) mm and then at a certain test temp (212F) ends up at (x+y) mm where y is the amount of expansion....

b

Where can we get new thermostats?

The air we breathe is mostly Nitrogen and if it is a vacuum, that would be devoid of any air. It has to have some air in it if that is what is forcing the bellow expansion and contraction.

I spoke to guys at HPH and they have some at a reasonalbe price and I also heard Jake has some. Would be nice to get some new ones?

I have repaired them before. there is not a spring in there, just air. put it in a vise and re-solder teh top