What would cause a thermostat to lock open?

[01TJ-Blues]

Ok all you cooling system wizards. What would cause a thermostat to lock open? I’m on my third Stant 195 now and befuddled.

 

[Jerry Bransford]

Improper installation? Or is Stant now also making "failsafe" models? Failsafe thermostats are well known for failing too easily in the open position.

 

[01TJ-Blues]

For certain they have been installed properly so that isn’t the issue. These all had the lock open tabs so I’m curious if Stant makes them without the lock open feature as well.

 

[Jerry Bransford]

What is the model # of Stant you have been installing?

 

[01TJ-Blues]

Yes, all three were the same, I’ll grab the box and check the part number shortly.