Buzzer of Doom - oil pressure control unit

[gailus40]

1.9DG autobox.
The buzzer of doom has tormented me for months - very predictable, only shrieks when the revs drop as I slow down when the engine is hot. Every time the revs drop, it buzzes. Will never do at stationary, when idling or when revving, or allowing the revs to fall, only when under load, ie moving.
Pressure switches have been replaced with the correct Brickwerks one, pressure has been tested hot and cold and is good. The oil pump seized in Dec, replaced that, and she still buzzes. Every thing else has been double checked, oil changed, pressure retested etc, and think it must be an electrical fault. Am having oil pressure and temp gauge fitted tomorrow, just for peace of mind and cos I've had enough of the Buzz. I think it's probably the regulator behind the speedo (Oil Pressure Control Unit) that is faulty, so have bought a new regulator from Maplins - getting my garage to fit it tomorrow, but can't find a pic or diagram or instructions how to do it - they haven't done one before. Can't find it on your wiki - and I would be grateful if anyone could help. I can find instructions/info on the oil pressure system - except for the OPCU, and the wiring behind the dash.
Cheers

[itchyfeet]

Ground the switch wire at the dash end where it goes into the multiplug it it stays quiet its not the dash, don't want to be messing with the dash unless you really have to, best prove it first.

Buzzer only sounds over 2000rpm

my engine is getting old now and buzzer will sound when very hot coming into roundabouts etc on 15/40 mineral I have to run 20/50 mineral which is thicker to stop it, I suspect ths pump failure put some wear on things and you need a thicker oil and check it's mineral.

[marlinowner]

This is almost certainly low oil pressure due to worn bearings. I had exactly the same. For some reason people (including me) think that when the oil pressure alarm goes, the last thing it could be is low oil pressure. Fitting a guage will be interesting, you will be able to see the effect of going to a thicker oil.

[ghost123uk]

I think it's probably the regulator behind the speedo (Oil Pressure Control Unit) that is faulty, so have bought a new regulator from Maplins

Me thinks you may be getting things a tad mixed up there. The regulator you get from Maplins (assuming part number 7810) is the 10 Volt regulator for the fuel and temp gauges and has nowt to do with the buzzer of doom. (by the way, that one is dead easy to DIY fit).

Every time the revs drop, it buzzes

There may be some additional info coming your way on here re that ^^^ = watch this space.

This is almost certainly low oil pressure due to worn bearings. I had exactly the same. For some reason people (including me) think that when the oil pressure alarm goes, the last thing it could be is low oil pressure.

^^^ Too true

[gailus40]

Thanks for all the answers -
I bought that Maplins regulator, as it was the answer I was given when I asked the question on another forum. At least that is only a £1.09 loss, and the garage haven't fitted it yet. Phew.
Gauges are going in this morning. Stationary, whether hot or cold, the pressure test are good at idle, high revs, everywhere, and you can never make it buzz. Does this mean it is likely to be worn bearings? We didn't think so as she sounds and runs fine - even with a stethoscope on the block when running you can't hear any bearing sound? Thicker mineral oil going in today - just had come to the conclusion it must be the control unit, as we thought we had jsut about ruled everything out, and if this unit were replaced, it would rule out electrical fault.
Any one know where I can get an OBCU?, and how to change it?
Many thanks for your help

[marlinowner]

When the van is stationary and hot, ie cooling fan cutting in, the oil won't be as hot and hence as thin as after a few miles at speed. I have an oil temp gauge and the oil is noticably hotter during a motorway run. Buzzer coming on when decelerating eg at end of motorway slip road is classic for this. So when the gauge is fitted you will be able to see if the oil pressure is above 2 bar (or whatever the rating of your oil pressure switch is) next time the buzzer sounds. Don't worry about other possibilities until you know what the oil pressure is under above circumstances.

[gailus40]

Cheers. Yep, that's the point I'm at - waiting to get the van back and do a healthy test drive - it will soon be obvious. It was only that 2 people have suggested it will definitely be worn bearing - I just don't see how (yet), as there is no real evidence for this. Fingers crossed. I may be back on here crying tomorrow, lol

[itchyfeet]

Buzzer operation explained here
http://www.brick-yard.co.uk/VehicleSpec ... fo/dop.htm" onclick="window.open(this.href);return false;

it should not sound below 2000rpm, do you have a tacho?

I have just tested mine, disconnect switch with yellow wire and slowly raise revs, held at 2000 it does not go off, raise to 2100 and it triggers after a few seconds
reconnect it goes off.

[gailus40]

Yeah, I'd already read that. Pressure gauge and rev counter just been fitted today - not test driven it yet to see what actually goes on under load. I've never been able to make the buzzer trigger when stationary, and pressure tests have been good at idle and high revs. Will have to see what it does when I get to drive it (not got it back from garage yet). Anticipation is killing me.

[ghost123uk]

From your pressure tests, perhaps it is sounding less likely to be bearing wear now, though the comments above about just how hot the engine is remain relevant. Even so, many on here have found that the 20/50 mineral oil may well help if it is a slightly worn bearing/pump issue.

[gailus40]

Thanks everybody - never got to sort the buzzer as couldn't find a replacement OBCU - so just disconnected it. Running quite happily on the gauges of truth. I put 20/40 mineral in it (I think), and she is now running hot on the oil - get up to just over 100. Little bit concerned about that, but hey, she is actually running, and her oil pressure seems to be just fine.