The oil pressure light has not been extinguishing on the Sunbeam S7 Deluxe. I removed the switch and put some pressure to it, which did not open the contacts. The stamp mark on the body of the switch is 10psi. I was well above 10psi air pressure and the switch did still not open.
Figuring that there are replacement switches available, it would not hurt to try to take this one apart to see if it was repairable. The switch was not leaking oil, so it seemed reasonable it may be just something with the contacts preventing it from opening at the correct pressure.
The adjustment pin has a slotted head inside the electrical contact stud and would not move.
There is a pressed sheet metal collar around the switch body. I put it in the vice and began prying at the collar. It eventually slipped up over the switch body and exposed two cutouts with a view of the contacts. The diaphragm pushes against the outer contact which lifts it from the fixed contact. The fixed contact was initially factory set at 10psi, and then fixed in place with a center punch mark. This explained why the adjustment would not move.
After cleaning the inside of the contact chamber with contact cleaner, I was able to see it operate. Using two small flat bladed instrument screwdrivers, I could hold the fixed contact against the adjustment pin and slightly bend the profile of the contact. A few iterations of this yielded a nearly perfect contact break point just around 10psi.
The tool I'm using in the video is a continuity tester. It has a small buzzer and battery in series. The pointer end is connected to the buzzer and the other side of the battery is connected to the wire clip lead coming out the back. I built this long ago for general electrical testing.
(Forgive the state of the workbench, I usually don't leave it that dirty.)
If it continues to act up, I will probably order a new pressure switch. For now at least I know how the original switch works.