Testing DOPWS

[Snowmark]

I have never heard the buzzer of doom.....and therefore the pessimist in me suspects that it isn’t functioning.
I have recently put a DG engine (late) in the van which doesn’t have great oil pressure (according to a dash mounted Oil Pressure Gauge).
I would like to check that the buzzer actually works - after reading the Wiki, am I right in thinking that if I disconnect the pressure switch from behind the water pump (the High rpm switch) and just leave the wire hanging so not earthed, that this will simulate an open switch and sound the buzzer if the revs are above 2250rpm?

Feel free to correct my stupidity. Thanks for any help


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[itchyfeet]

yes that's a good test method but it takes a few seconds to trigger.

your high pressure switch would need to be below 0.9 bar at 2000rpm to sound the buzzer and that's very low, yours is just slightly low.

[937carrera]

The test you propose will test the wiring. Earthing the wire should then silence the buzzer

While many have the 0.9 bar switch, some had a 1.8 bar switch and there's an option for a 1.4 bar switch, so given the age of the van any of those three could be in place now.

https://www.brickwerks.co.uk/brickwerks ... -switches/

Mine was a bit low and went off when the oil was hot, so I replaced the 1.8 that was fitted with a 1.4 for silence and retention of the warning system

[Snowmark]

Hmm, I hate it when the pessimistic me is right......Took the wire off the switch under the water pump and left it suspended. Ran the engine and kept the revs at approx 3000 - nothing. No buzzer, even after about a minute and a half.

And then I noticed some steam and it had decided to eject one of the temperature senders from the thermostat housing so I lost all my coolant. I can only assume I hadn’t fitted it correctly when I refitted the engine so only have my self to blame.

Meant that DOPS testing was put on hold for the afternoon


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[itchyfeet]

[itchyfeet]

It's been disabled, either...

A) the wire was grounded somewhere between dash and the switch
B) The green tacho wire to dash has been disconnected, no tacho feed no buzzer.

Clocks could be faulty also.

[Snowmark]

Well that could explain it as someone (me) may have commandeered the green wire to feed a dash mounted Tacho.......

I was half having this thought as the steam started to rise


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[itchyfeet]

Well that could explain it as someone (me) may have commandeered the green wire to feed a dash mounted Tacho.......

T into it the dash still needs the connection , how do you think it knows the engine is above 2000rpm?

Wago 222

[Snowmark]

Obvious when you think about it. I shall do this tomorrow once I’ve bled the coolant, adjusted the brakes, cleaned the valves, boxed up my spares updated my engine build thread


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[itchyfeet]

for a sensor to pop out you must have forgotten the clip or have plastic one that broke, the metal are best but not sure if you can buy them anymore.

[Snowmark]

Haven’t had chance to investigate as I’d just been on a 20min test drive so the coolant pouring out was quite hot.....

It was a plastic clip ....I shall discover more tomorrow when it’s cold and the floor is dry


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[itchyfeet]

somebody must still be making the metal clips

https://volkswagen.7zap.com/en/rdw/typ+ ... -16007/#19" onclick="window.open(this.href);return false;

032 121 142

[Highroller]

I had the coolant sensor pop out after a partial rebuild and had used a plastic clip with an older sensor. I managed to find a metal clip and I've had no issues since.

[Snowmark]

I now have a functioning DOPWS - reinstated the green wire to Position 9 in the multi plug, disconnected the wire to the oil pressure switch, revved to 3000 rpm and got the red oil light and a noise like an angry wasp (was expecting it to be(e) louder....).

My only concern is that it will now actually sound as the DG appears to have poorer oil pressure than first thought. It only needs to function for 2 months so fingers crossed


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[937carrera]

Did you find out what switch you had ?

I recall it was a 1.8 bar one, so either get a lower one or earth the wire. The dizzy has a handy spade