Oil Pressure Warning

[craigt]

I should have done this years ago and I'm sure many will have already.

I've just fitted a small but loud audible warning to the low oil pressure warning light circuit in my SC. Took 10 minutes.

When I bought my first SC 6 years ago I inspected the car as best I could with the limited Porsche knowledge I had at the time. I drove it over 300 miles home and it ran sweetly. The following day I inspected the car up on stands and was horrified to see the 2 rubber oil hoses at the oil tank were severely perished ( how did I miss that).

Although I always keep an eye on the oil pressure, I feel that if a hose let go it would be too late before I noticed the gauge. An audible device will give instant warning and allow me to shut down the engine before damage is done. Something I hope I never use but provides a little peace of mind.

[Ian Comerford]

Not a bad idea.  Do you have any details of what you did, parts, wiring etc?

[craigt]

I'll post some details later today 

[David Gander]

Sounds like a very worthwhile addition for piece of mind.

[craigt]

This is the warning "buzzer" - £1.99 on ebay. A pretty sharp noise similar to the low brake pressure warning on an LGV. No point in it being a nice soft fluffy sound!!

 

 

Initially it was fitted behind the gauges but i felt that at speed with the top off and the engine howling I might not hear it so I extended the wires to allow it to be fitted outside the dash in the cabin.

 

 

Remove the low oil pressure warning "OEL" bulb from behind the gauge. The green/white wire is earth - the red/black wire is positive on my car (best confirm +ve and -ve for yourself).

 

 

Solder piggy back spades like these to the warning buzzer ends, this way you're not chopping into the wiring loom and it can be easily removed if you don't like the result.

 

 

I removed the mirror control switch and passed the wires up behind the gauge so that the buzzer could be mounted under the dash so the sound couldn't be missed. I filed a small notch out of the mirror control switch hole to allow the wires to sit properly and allow the switch to be replaced.

 

 

Now connect the buzzer piggy back connectors onto the bulb holder, it doesn't matter what goes where.

 

 

Reconnect the cars green/white cable to the black connector of the new buzzer and the cars red/black cable to the red connector of the new buzzer as shown below.

 

Test and refit the gauge. The buzzer will still work even if the bulb was to fail. Only failure of the pressure sender or wiring will prevent the buzzer sounding.

 

[Leicestershire]

Great idea but also worthwhile changing the pressure switch to a higher pressure or adjustable pressure type. The standard Porsche item closes when the starter motor turns the engine over. If the warning bulb illuminated at high engine speed the damage has been done.

[craigt]

Damn, was that a waste of time then 😭

Aren't the pressure switches matched to the gauges? If you fit a different switch will the gauge read wrongly

[Leicestershire]

The sender near the fan controls the gauge. The sender at the flywheel end controls the bulb.

The modification you have made is often used on classic competition cars. For it to be of any use you end up with the buzzer sounding when the oil / engine are at operating temperature and the engine is at idle. This is not an issue on a competition car but would get a bit tedious on a road car.

[993porky]

Hi @Leicestershire  after a bit advice on this please if possible,my car is 85 and just got back on road after a long lay up.

when I first turned key only battery light came on no oil(can) light, when looking in engine bay I noticed what I now know as oil pressure switch was disconnected, why I don’t know it’s the one at back of engine, so I squeezed hand around and plugged it back in,turned key and great  the oil light came on with battery light so fired car up expected light to go out with battery light but it didn’t, so is it possible the oil pressure switch needs replacing ?

I’ve included a picture of the part to show what I mean

thanks 

Paul

[Leicestershire]

Paul,

Is your pressure gauge working OK and you have good oil pressure at startup and when the oil is warm?

The switch could be at fault. You could test with meter across earth and the terminal - rig up some long wires so you can watch the meter as you start the engine - however all a bit tricky with the standard EFi gubbins fitted.

Also consider that the wiring could be damaged or just wired up wrong. It does read like a previous owner / trader has pulled the plug on the switch to 'fix' the problem.

After many years of playing with air-cooled 911's I have not seen many of the rear switches fail without evidence of impact damage. Most cars are still on the original and your '85 car is a relatively young beast.

The pressure sender near the fan however fails with some alarming regularity - usually just after any warranty expires on the part - one of the few parts I buy the low cost UFI option instead of genuine or OE brand.

 

[993porky]

Thank you @Leicestershire for your thoughts, I believe pressure to be ok but I’m a bit new to this, gauge goes up.

I mentioned it today at the specialist when I dropped car off for something else which is one of my posts “strange whirring noise”

so hopefully car will come back all sorted, off topic but on your above photo what actually is the CIS temp switch ( what is CIS )

thanks

Paul

[Leicestershire]

I borrowed the photo from the web just to show the position of the oil pressure light switch as you will be working blind with the efi still in position.

The CIS temp switch is something relating to the previous generation of fuel injection fitted on pre '84 cars don't know what the later cars have.

CIS = Continuous Injection System = Bosch K Jetronic.

 

[993porky]

Thank you for that @Leicestershire 👍🏻