Club 80-90 Forums

Okay, finally found a suitable earth. But the buzzer still comes on once I rev over about 2500. Checked the wire and it’s sound. So what now? Is it the ground at the dash (anyone know which one?), or the little solid state part in the clocks? Why would it still sound if it’s been grounded?

All you need is to make the circuit, holding against an earth is fine for testing, you'll need a helper

Had another go this morning. Cleaned up the end terminal with fine sandpaper, then did the same to the ground (a screw hole in the luggage area), Screwed it back down. Took the clip apart (that joins the two oil pressure cables to the main loom, in the engine bay), and did the same for them. Started it up, revved to 3500 - no light or buzzer. Result.
So what does that prove? That the circuit may have been compromised by dirt and grime, and now it seems okay? So ideally, what I have to do now is reconnect it to the sensor/switch, and it stays off, then all is well? But if it buzzes again, then the switch is faulty? Is that right? Think I may need to replace the last stretch of brown cable, as it’s a bit melted in places. It’s also going to be a bit tricky keeping it away from the fan belt....

Great, that's progress

What you've proved is that the DOPS wiring / buzzer is fine. When the wire is earthed the buzzer is silenced.

That leaves three possibilities:

1. The wire was grotty, clean / replace it, put it back on the switch and see if it stays silent when revving over 2000 rpm
2. If you replace the wire and the buzzer sounds then it could be the pressure switch that has failed, so needs replacing
3. You really do have a low pressure oil problem, get the pressure checked

Probably just 1, if not then hopefully it's number 2.

When I replaced the spade on mine I fitted the spade to the wire and then bent it to 90 degrees, that way the cable should stay clear of the belt. Even better if you have 90 degree or side feed connectors (see earlier picture for OE design)

Went to take the bus to the MOT station today (had to cancel last week, because of the buzzing buzzer), and guess what - it wouldn't start. Sounds like a classic flat battery. Hope it's nothing to do with my temporary buzzer-stopper fix. So had to cancel again...

Putting the DOPS wire to earth shouldn't drain the battery, the circuit it only live when ignition is on.

Can you jump the van off to go for the MOT - it'll probably be fine once it's been running for 20 minutes.

The DOPS buzzer isn't an MOT test point, too late now, but you know for next time.

If I'd had my wits about me, I could have used the leisure battery to jump start it. It hasn't moved for a couple of weeks, so it's possible it's just a flat battery. It usually starts first time.

Sorry for the thread revival, but the problem has reared its head once more.
You may recall that I had a problem where the buzzer of doom was going off. Well, after much investigation, oil and filter change, etc, it stopped. Oil pressure is good.
Then it (the buzzer) started again, and because my garage man assured me the engine was fine, we agreed it was safe to ground the sender wire (to stop the buzzer), and change the sender next time the van was in the garage.
Okay, all sort of good so far, but over the last few days, the buzzer has been coming on again. Now, bear in mind that the sender lead (to the front sender) is grounded.
The buzzer is coming on, with the red oil light flashing, when I go over 2200 revs. I thought that grounding the sender cable would automatically stop this happening?
Why is it waiting until the revs reach 2200, when the high rev sender is 'out of the loop'?

The engine sounds fine, and seems to pull well enough. It looks/sounds like an electrical issue - so where do I start? And why on earth does the buzzer sound over 2200, when the sender is not connected?
This is driving me mental, to be honest, and really puts me off driving the van.

Sounds like the connection that normally goes to the "high" pressure switch, and was earthed, has come off the earth, so it looks as though there is no oil pressure to the buzzer module.

The DOPS circuit only becomes active at ~ 2000 rpm

The "approved" method is to connect the wire that goes to the pressure switch to an earth spade either on or next to the distributor.

I drilled a hole in a panel, and used a self tapping screw to fix the cable to the ground (straight through the clip).

Oh

I think you had better put a photograph up, not too close, so we can see where the cable you have earthed comes from and is located.

Just to say that this noise occurred on my bus whilst my daughter was using it for her hols. A quick look around, aiming to quieten the buzzer, showed a break in the printed circuit flex going to the actual buzzer. As the vehicle returned from Cornwall, only to go straight off to Yorkshire for a full body resto it is still just disconnected at the back of the dash. A job for the future.
Perhaps somewhere else for you to look.

Let me check that I understand the way it works...
The warning unit takes the signal from the low-revs/low-pressure sender UNTIL they go over 2000ish.
Then the unit takes the signal from the hi-revs/low-pressure sender (the one by the water pump).

So all is okay here until the revs hit just over 2000. Then the buzzer comes on (a continuous buzz) and the red oil light flashes.
BUT.....the cable is grounded, via a self-tapper in the luggage bay. So what's the problem?

Possible ideas....fault in wiring, screw not earthing properly, anything else I can look at? Something in the dash pod?

Not quite

There are two circuit

Original "low" pressure circuit, ~0.3 bar, switch between the pushrods, simple on / off switch approach to warning light

DOPS circuit using a "high" pressure switch, say 1.8 bar, connects to a bit of electronics that soind the buzzer if the pressure is lower that 1.8 bar when the revs are over 2000

More detail here

http://www.gowesty.com/tech-article-details.php?id=42

I'm not sure you have grounded the right cable, a picture's worth a thousand words as they say.

you need to continuity test your wiring from the earth in the engine bay to the 14 pin connector, if that is fine then it must be either the 14 pin connector or the track the 14 pin connector connects to or a fault on the circuit board

if you have rev counter then the rev counter signal is split and the track actually runs over the edge of the folded foil where the connector attaches - but since the bod goes off you know that you are getting a revs signal to the bod circuit

have you got the shroud for the 14 pin connector fitted and is it all still intact (it plugs through the foil holding the foil in place and makes the connection more rigid - often the shroud gets removed and not put back so the connector is only making physical connection to the flexi board via the sprung contacts and all the vibration can cause the track to become worn and thus you loose your connection, especially if the plastic tongue the foil is folded over gets broken as there is nothing stopping it vibrate

the low pressure sender is closed no pressure opens at 3.6psi so when you turn the ignition key the oil light comes on and once you start the oil light goes out once the earth potential disappears


the dynamic oil pressure system only works above 2000rpm, if the revs signal from the coil or the alternator (petrol/diesel) is over 2000rpm the circuit looks at the high pressure signal, ie looking for earth potential, if there is earth potential because the switch is closed (ie you have oil pressure of 0.9 or 1.4 or 1.8bar depending on which switch is fitted) or the wire is grounded the buzzer will not sound, if there is no connection the buzzer goes off, so if your wire is grounded and tests out as grounded at the 14 pin connector then the issue is there or in the foil or the bod circuit

if there's damp behind the dash then corrosion may mean that tarnished connections are not making good contact, the bod circuit is behind the speedo and there is a 5 or 6 pin connector onto the pins even that could be corroded enough to provide some resistance that fools the circuit making it go off

my best guess is either your earthed wire isn't actually earthed or the 14 pin connector is not making good contact on the high pressure contact, pin 122 iirc, could be 13 they are labelled in german