these valves are mostly located out side in new england, all positioners are rated class 1 div. 1 and sealed appropriately, most actuation of these valves, happens in the winter, and therefore most failures also occure then. However, this is not always the case. We have had failures in the summer months as well. I've measured resistance across a new switch 0.0 Ohms, and a failed switch 20 ohms, on the normally closed contact. I can watch the contact make and break with my meter, but the resistance of the contacts is too high. The contacts them selves are in a hermetically sealed housing, located in a gas filled, vac tube. so moisture is not a factor