Yellow Diamond Electrical Control System
Oil Pressure Switch
Description
From the BUT A Series Service Manual:
The oil pressure switch is mounted on the engine casing extension and operates the oil pressure indicator lights on the control panel situated in the driver's cab.
Schematic
The schematic taken from the BUT A Series Service Manual shows the electrical connections to the swiches, one on each engine. The common feed to both is "Train +", when the switches operated this is connected to the "Oil Pressure 1" and "Oil Pressure 2" circuits.
Those two circuits are connected to one side of the appropriate bulb on the cab display - the other side of the bulb to "Train -", and also to the jumper sockets.