I agree with this one. Also since you said it was blue and round, I bet it is an eai switch like someone else said. And they do not have a pressure differential in them. So even as the air cools in the tank, or the outside temp drops, it will start the comp back up. Those pressure switches are best used for engine driven comps.SlammedDime said:What kind of adjustable presssure switch??? if its a kind like what AIM sells, not a square d one, then it kicks on at a 1 psi drop... so if you have ANY leaks, it will always be on.