Oil pressure switch

[His Dudeness]

Yeah normally open so the reed switch does nothing until the float drops so the reed switch is unlikely to fail due to wear. The one I looked at, the reed switch was working fine but the small circuit board that the reed switch is soldered onto was corroded due to water ingress and the track in the circuit board was completely gone so the circuit was always open even when the reed switch was closed. You'd never know that the circuit had failed open unless you checked if the oil light had come on during an oil change. The check that happens when you press the starter switch just shows that the bulb is working not that the oil level switch is working because when you press the starter switch it grounds the bulb through the starting cut off relay not through the oil level switch. I bet there are loads of corroded oil level switches but it goes unnoticed.