new air filter temp sensor doesn't work

[ru469]

I have a 85 chevy c-10 with a 305 and 4 barrel quadrajet. My old temp sensor in the air filter would close the snorkle valve but wouldn' t open it when it warms up. So I bought a new sensor and it does the same thing, the vaccuum closes the valve from the outside air and never opens. What could I be doing wrong? I've changed the direction of the sensor and swapped in and out going lines from the sensor. Any help would be apreciated.