I have a problem with my A/C thermostat that I am hoping someone can help me with.

The thermostat is a spring loaded switch that has two inputs that balance against eachother: the **** and a tube that goes to the evaporator. While working with the evaporator I broke the end off of the tube. My questions are:

Is it simply air under vacuum, or another gas?
Is there a way to fix it? (heat the tube in an oven and solder the tip closed maybe?)


Thanks,

Bob