DOPWS - Flashing lights but no buzzer

[T25Convert]

Right lovely people, I is confused (not for the first time!) Read the wiki but hasn't helped.

I have 1.9DG engine, late model with the buzzer of doom. I have (not wishing to sound smug) a very nice and clean PCB with good connections. I was staggered too.

The oil light flashes all the time, when you turn the key, at idle, flat out, hot, cold etc etc etc. No buzzer above or below 2500 rpm (not that I have a rev counter) - it does make noise though if you connect it direct to a power source.

Oil pressure itself is fine, so its all in the wiring.

Oil pressure switches are both black, so that doesn't help me identify if they are correct, although I think this is a red herring as it should turn the buzzer on above 250 rpm if they are both wrong.

So I reckon its an issue with it knowing engine revs - where does it get this from? Any other thoughts??

[Aidan]

you have the wrong switch fitted in the low pressure port you need the blue one 028 919 081 D between the pushrods

the switches switch in opposite directions, so blue is closed switches open circuit when engine starts and light stops flashing, high pressure switch is open and closes at correct pressure and bod checks that it is closed only at 2000rpm

[T25Convert]

you have the wrong switch fitted in the low pressure port you need the blue one 028 919 081 D between the pushrods

the switches switch in opposite directions, so blue is closed switches open circuit when engine starts and light stops flashing, high pressure switch is open and closes at correct pressure and bod checks that it is closed only at 2000rpm

Thanks, so if I pop the wire off the 'low low' switch so its open circuit, the light should go off?

Fingers crossed for the easy fix!

[Aidan]

yes, I think, if you disconnect the low switch you will loose the flashing light from the moment you switch the ignition on
double check the continuity of the switch it should be closed with engine off
I don't think it will affect the self test of the BOD circuit, but it might, so worth disconnecting the double connector and revving to over 2000 to see if bod circuit operates

[AngeloEvs]

The DOPs low pressure and high pressure circuits act independently. Only the high pressure section of the circuit monitors RPM against the condition of the higher pressure switch. Disconnecting the low oil pressure switch will not cause the buzzer to sound and will only affect the Red LED operation.

[T25Convert]

Closer inspection showed it wasn't a black sender (whoops) but a blue one wearing a very tight runner jacket.

However, removing the jacket released a mini fountain of oil. The sender is blue, and looks virtually new, but has failed where the plastic is crimped into the metal. All that was holding the oil in was the rubber dust cover.

Narrow escape here I think, would have been easy to loose all the oil.

With it all cleaned up it works a small intended, just need to get a new higher quality switch.

Cheers all.

[Aidan]

we seem to be seeing a lot of switch failures these days, old genuine ones seemingly end of life and fairly recent replacements not for quality which is a bit worrying, but some of it may be due to engine work/swaps by heavy handed mechanics or using engines pulled, stored, shipped by heavy handed breakers and people being rough with the wiring which was originally cable tied to the senders when factory assembled, so it may also be cable tying the connectors may or may not contribute to the issue, all so much easier with engine out but can be awkward both to fit and to remove when in situ work being done

[T25Convert]

we seem to be seeing a lot of switch failures these days, old genuine ones seemingly end of life and fairly recent replacements not for quality which is a bit worrying, but some of it may be due to engine work/swaps by heavy handed mechanics or using engines pulled, stored, shipped by heavy handed breakers and people being rough with the wiring which was originally cable tied to the senders when factory assembled, so it may also be cable tying the connectors may or may not contribute to the issue, all so much easier with engine out but can be awkward both to fit and to remove when in situ work being done

Around 2000 I was driving a Mk1 golf, which blew an oil pressure switch - on this the plastic split around the contact. There was much hand wringing at the time about quality of these senders, where the plastic seemed to have been cast in two halves which split at some later date. This tended to mean the switch broke and the light came on pronto.

However, modern ones seem to be failing around the crimp, which means the oil light may or may not come on straight away. Quick google suggests there isn't much to choose between the various suppliers, they are all seem to have people claiming failure.

As you say, careful installation and minimizing any external loading would seem to maximize the chances of it surviving.....