Oil pressure light

[Hej-Hej]

After changing the engine oil and filters on my '02 Ford galaxy 1.9 TDI 115, i noticed the red oil warning lamp light up at "ignition on" but then it goes off along with the airbag light, yet without the enginge running.
Will a bad connection for the oil pressure sensor or maybe a faulty sender cause this to happen?

[johnnyroper]

Only thing I can think is faulty switch or wiring.

If memory serves correctly the sender grounds the wire when it sees pressure to turn light off.
So in theory you could pull wire off when engine is running to test wiring back to dash and see if it puts light on. If it does then that would point to faulty sender switch being stuck in closed position.

But vw OPS circuits are not a straight forward wire to bulb set up,the signal is interpreted by a control unit that puts light on or off depending what signal comes back from sender.

[insanitybeard]

My Galaxy also exhibits this behaviour, I've never investigated further to determine if it's abnormal!

[Hej-Hej]

Ok, actually i thought the sender would ground the lamp to turn it on, but if opposite i think it's most likely to be a faulty sender then. Anyway i will have a look at it, trying to pull off the connector and see how it reacts. Will post back when i find what is cauising this problem and how it was fixed

[johnnyroper]

Checked mine and found it is same as yours,seems it's normal operation as there is an input from alternator to the oil pressure control in instrument cluster. I also did not realise PD lumps have high pressure switch that is normally open but closes at 1.5bar to give oil pressure light and a buzzer.
The low pressure is normally closed but opens at 0.3 bar rising.

So it seems oil pressure light only does a self test with ignition on then goes off.

[Hej-Hej]

Thats interesting.. Would be nice to know if every Galaxy just make this self test of the oil light when ignition is turned on and then goes out.
Think its a very important thing to work as intended..

[johnnyroper]

Know what you mean about it being very important thing to work,I am gonna try unplugging mine while running see if it gets the warning noise and flashing oil light. In theory it should as low pressure wire will not be grounded while unplugged.

[Hej-Hej]

Exactly.. Would be great to know how yours reacting to the plug not connected, will try the same thing with mine just have'nt got the time to look at it, as im at the hospital with my wife and new born baby girl at the moment

[Hej-Hej]

So.. Unplugged the connector from the oil pressure sensor and nothing happened! Exactly same bahaviour as before, light up on ignition ON, then goes out and stays OFF even with engine running.. Think i'll try with a new sensor if there's any difference, seems very wrong to me!

[insanitybeard]

Yeah that seems a bit worrying, could all of our oil pressure sensors be dodgy? Must be a very common issue if so! Are any other members able to see if their oil pressure warning lamps behave in the same manner as ours do?

[johnnyroper]

That is worrying I have not tried mine yet will have a go later.

Also there is an rpm input to oil pressure control,looks like oil pressure warning does not work below 1500rpm?? Maybe try raising engine revs above 150" while disconnected see if warning sounds then?

Very odd system if works like that as engines with no pressure still seize below 1500 revs!!

[johnnyroper]

I unplugged mine today and also found no light on when idling or if raising rpm up...
Didn't have much time to mess so going to try grounding it when running when have a spare 10 minutes in case it works opposite way.

[Hej-Hej]

I also had mine unplugged again today and tryed raisin the RPM to 2k, still no light or warning. Also did some measuring with my Fluke and when engine off, oil pressure switch is open -no ground on the pin in the sensor, when idling switch is closed and grounds the pin in sensor. Also theres no connection to ground in the plug for the sensor when not connected so i dont think its shorted and the oil pressure switch dont seems faulty as i first suspected.. I really cant figure this out!!

[johnnyroper]

It's a very odd system we can't both have same faults??

I wonder if the other switch comes in to play at low pressure also?

So when testing if oil pressure is good wire is grounded via the switch,do it should throw oil light if disconnected unless the second switch does act as a back up for low pressure aswell as high pressure fault?

[Hej-Hej]

Do you know where this other switch lives? I only know of the one that sits in the oil filter housing (no 17: http://eucatparts.com/?action=cat_ford_part&s_id_part=24864&s_id_model=99&s_code_image=D002117504 ) but i really think it should throw the oil light if either one of the switches fails. Hope to find an explanation or an solution to this problem!

[johnnyroper]

I think it's down by oil pump/timing bet area.
You and me both I am hoping to find some more info about the vw dynamic oil pressure system to see how it works

[Hej-Hej]

Yeah that would be great, will try to find that other switch and unplug both of them at the same time see if that triggers the oil light

[Mirez]

It will, the system is actually fairly clever. Using a high pressure and low pressure switch to work out the actual value. The 1500rpm (in reality its closer to 1800) signal simply tells to the cluster to look at both sensors. Since below 1800rpm we really only care that we have SOME pressure, after 1800 we need to ensure we have GOOD pressure. By utilising the sensors in this way the system can alert you to both a very low pressure problem but also that its not generating enough pressure.