Printed Circuit

[Camper90]

Does the light/buzzer come on if you disconnect the other oil pressure switch and rev the engine above 2000 rpm?

no, still the same

[marlinowner]

If the buzzer doesn't sound when you rev over 2000rpm and the sensor is disconnected, that suggests a problem with the BOD circuit. If the other instruments are working then 12v supply to instruments is OK, check for 12V at the buzzer circuit built into back of speedo. If that is OK (continuity between pin 8 of the 14way connector and one of the buzzer circuit pins, shown as J114 pin 15 in Haynes) then the problem is most likely with the circuit in the back of the speedo, not the PCB itself. If you can work out which of the BOD pins connect to the low pressure oil switch (14way pin 13) and the oil pressure warning light, and connect them together, then the oil pressure light should come on with ignition and go out when engine started.

[Camper90]

Does the light/buzzer come on if you disconnect the other oil pressure switch and rev the engine above 2000 rpm?

Not had time to check yet, do you know where the buzzer of doom is, behind the dash?

[marlinowner]

Its built into the back of the speedo where the PCB connection plugs into it.

[Camper90]

Its built into the back of the speedo where the PCB connection plugs into it.

Thanks, I will try what you said asap.