Buzzer of DOOM. Problem at dash end.

[KarlT]

Problem is a Dash end. but PCD looks pretty good.
Oil light doesn't come on. Nor does buzzer. Swapped bulb but still no go.
What do I look at/test on PCD?

[Syncro G]

take it when swaping the LED you tried it both ways as they are polarity sensative.

DOP system testing in a rather handy green bible...




If you do have to replace the DOP control bord they are petrol/diesel spacific so they get the right RPM signal to trigger on.

[KarlT]

No, I didn't turn it round!

Is that all from the Bentley? Got to get one of those. Thanks for taking the time.

Where exactly is the buzzer?

[Aidan]

behind/inside the speedo.
no oil light with ignition on engine not running means the low pressure switch is not connected to the pcb (or bod circuit faulty maybe), if it was then the light would flash and then go off as engine starts and pressure goes over 9psi iirc. Then the bod circuit uses the high pressure switch in combination with the tacho signal from the alternator(diesel)/coil(petrol) to check that you've got minimum of 1.6 bar at 2000 rpm or above, if you don't have then the bod will buzz, and light will flash (or the bod circuit maybe faulty)
If the high pressure switch wire is earthed out (deliberately or wiring fault) then the buzzer will never sound regardless of what the pressure/revs are.
i.e. if you are trying to sell a stuffed engine you disconnect the low, wire the high to earth and hope the buyer doesn't know that the oil light should flash before start up.

[KarlT]

Cheers Aid,
Yeah, I know that story......
Anyhow, Have taken off original Dash/PCD/Bod. Looked in really good condition but Oil light didn't come on.
Put on one from one of my other buses, which I know to be good.
Turned ignition....oil light flashes, start engine....oil light goes out. Rev engine....buzzer comes on. Think its probably sender switch as it come on straight away even with cold thick oil, & I know engine isn't that bad.

Anyhow, I guess my question is.....If oil light bulb is gone/broken....Would the buzzer not work?

BTW....... what new high sender do I want? Are they classed by colour? (Sorry 2.1 petrol)

[Aidan]

simple enough to test the high switch, it will give continuity when op is good, 90% of time it is wiring fault. If you take the flag connector off the switch and earth it then rev the engine if the buzzer sounds it's a wiring fault, if it doesn't then it's the switch or the engine.

[bigherb]

If you have done all the other tests, check the diodes on the printed circuit its not unknown for one to go short circuit.