low oil pressure warning lamp

[7783911]

many articles on rennlist and pp but none explain the operation

should the light come on when first started (idiot light test)
how low does oil pressure need to be to light up

I had to replace mine due to PO mangling it and discovered this bulb holder for a 914 as a perfect fit



now the dumb question, dual post, does it matter which post the wires go to or is it the same and is just closing the circuit? (ground/power)

Thanks

Bob

[boyt911sc]

Bob,

When you turned the ignition switch to ON position (not START), the oil pressure indicator lamp/light would be lit because the oil pressure switch (normally closed) provides or completes the circuit. And when you start the motor, the engine oil will be circulated by the rotating oil pump and subsequently develops oil pressure in the system. This resultant oil pressure will turn the normally closed oil pressure switch to open and breaks the ground contact for the oil pressure indicator lamp.

When a running motor stall and stop running, the oil pressure inside the motor will drop and makes the oil pressure switch to close and complete the circuit to make the oil pressure indicator lamp to turn ON. Hope I am able to explain it well to be understood.

Tony

[HaroldMHedge]

The light should be on when the pressure is less than 0.1-0.3 bar.

[7783911]

thank you all

my light does not come on so i will test the circuit, i believe i can take the wires on the LP sender and touch them together to test the circuit (read on this forum somewhere). True?

[7783911]

ok, i never run out of dumb questions

how do i get to the low pressure sender to test it? I dont want to drop the engine!

[pete3799]

For starters you can test it at the light.
Ign. switch on check for 12v at one terminal and ground on the other (bulb should light).

If you're missing 12v but have a ground then the problem is not the sending unit.

[Walt Fricke]

If you have tested the bulb, and its +12 supply, and grounding the terminal where the wire heads back to the engine turns the bulb on with ignition on, then the switch is suspect. For grins, I'd open my electrical wiring schematic (you can find one on Pelican), and figure out which connectors this circuit goes through, and check each one. You will find that the circuit uses the large 14 pin connector back in the rear left of the engine bay. Identify this circuit there - if grounding there causes the light to come on, the rest toward the front is good. Then put an ohmmeter on the wire on the engine side of the plug and test for ground. If it shows an open circuit, you've pretty much verified it is the switch.

For access to the switch, search "partial drop" here. Access to it isn't easy, but it can be done. These switches are most often replaced because their internal diaphragm goes bad, or the crimp holding things together goes bad, and they leak oil. So it can be done.

[7783911]

I tested light and have power source but yellow green wire is not providing the ground. I am still struggling to find the switch and its wiring source if anyone has ideas on what I have to do to access that switch (i have 83 sc engine with CIS). do i have to remove alot of things to get to it?

[stownsen914]

Here's a thread discussing the location of the oil pressure and idiot light senders. I haven't personally worked on a CIS car. The idiot light sender may be a bit buried back there.

Wiring all the gauges in a 911 SC

[7783911]

tx stownsen, my question remains..is there a way to get to that switch while the engine is in the car and if so, what do i need to remove to get at it...so far no luck getting to it but havnt tried to see if accessible from below?

all...any advice welcome