944volks

Hi guys.
Newbie Porsche owner.
Always wanted one, finally thought Just do it!
I have a 1986 2.5 lux but with a S2 3ltr conversion.
After being on the road for 2 weeks the oil pressure gauge suddenly decided to point straight up to above 5 bar whenever the ignition was switched on.
Had alook at sender.
Cleaned connectors on sender. Bloody difficult to get to.
No difference.
Checked resistance of sender. 000.0 = No resistance.
Is it sender or gauge issue?

Thanks in advance guys.
Karl in the UK.

PaulD_944S2

"Checked resistance of sender. 000.0 = No resistance."

If you are saying that the sender has infinite resistance (open circuit) then the gauge will go to the max.
If you are saying that the sender has no resistance (closed circuit) then the gauge will go to the minimum.

You may have a bad sender.
Or a pinched or damaged wire between the sender and the gauge.

Disconnect the sender and tell us what happens.

944volks

Sorry, I might be saying resistance wrong.
When you turn multi meter on. It reads 1.0
put probs together it drops to 0.001
when I connect either side of sender contacts. It drops to 0.001
Doesn't that mean zero.... no resistance?


Gauge was working.
then one day suddenly went to above full pressure. , straight to top of gauge.
Have disconnected sender. Gauge still points straight up.
what do you think?

V2Rocket

aren't you supposed to measure resistance on the sender between one terminal and the engine block as earth?
i dont believe the two terminals are meant to be measured against eachother.

jspearin

An oil pressure reading of 5 bar no matter how warm the engine/oil is is usually a sign of a bad sender

944volks

Well I've checked resistance. .....
Across the contacts.
from each contact to earth.

All read 0.001 resistance.
what do the experts reckon.

PaulD_944S2

What does your meter show when the leads are not touching?
And what does it show when they are touching?
What ohms scale are you using?

944volks

Hi. Sorry for delay, just been living with faulty reading for a while.
i don't really understand the ohms rating.
I put multi meter on 2000. Should it be on 200?
where do I measure resistance between?
thanks k.

PaulD_944S2

Put your meter on 2000 ohms setting.
Read resistance from each pin to the case of the sending unit.

Coloradoguy

I'm having similar issues except my gauge is reading zero. Are the readings supposed to be taken with the car running, or with the key on, or off?

PaulD_944S2

Engine off, Key off.
Reminder: When working on electrical it's not a bad idea to disconnect the battery.

Coloradoguy

944volks. I'm dealing with a similar "No Oil Pressure Indicated" issue and would love to know what reading you're getting by measuring the resistance of the G terminal wire (disconnected from the sensor) to earth, with the ignition on.

In my case I'm getting a reading of 98.4 ohms and the dash gauge pins past 5. Darned if I know if this is accurate.

If it is, then I can feel assured that it is the sensor itself which is at fault. My new VDO sensor should arrive tomorrow and once installed would be happy to provide you with resistance readings for each terminal.

jeffro951

To do a simple test on the gauge and wiring if you remove the wires from the sender and ground each one at a time one will make the light illuminate and the other will make the gauge read max oil pressure. at that point replace the sender and you will most likely be fine.

trod944na

i'm also having issues with my 85/2 na daily driver. for as long as i have had car gauge pegs immediately when i turn key on, before i try to start engine, along with low pressure light (which goes out when engine starts). i disconnected blue/white wire from the G terminal, still pegs, disconnected DME interface plug near fuse block, still pegs, disconnected "O" fuse block plug, no pegging, but then almost everything is disconnected. i'm in process of disassembling fuse, hoping i can find short. also replaced oip pressure gauge just for grins and giggles