Oil Pressure Light '68 911

[68911USA]

Okay, so I'm troubleshooting some basics here now that I have the car in a drivable state again.

I've put about 1200 miles on this car since I bought it last October, including a lovely drive of about 1000 miles to get it home. Engine seems fine, no strange knockings or anything, and runs well from idle to redline.

I found soon after I got the car home that there was no bulb in the oil pressure light holder. After installing one, it lights up and stays lit all the time, even when I disconnect it from the sender on the engine. I replaced the sender, thinking that would fix it, but the light still stays lit. It does not waver with engine revs, just stays on all the time when the ignition is on.

From the way it runs, I really don't think there's anything wrong with the motor, and I would think that if it had no or marginal oil pressure things would have let go quite spectacularly soon after starting my original journey with the car.

So, all wiring seems to connect properly to both the gauge and the new sender, it's just a single spade connector on the sender on the engine. Is it possible that the mechanism that reads the pressure that the sender actually "senses" is what's wrong? Can anyone give me some idea of a way to troubleshoot this? Is there a simple mechanical pressure gauge I can connect to the electrical sender location to get a good oil pressure reading?

As always, I appreciate the help! I do have a loose '68 911L/S "temp/druck" gauge I could connect to it, if that would be deemed a worthwhile test, but I'm not sure how to wire that up, either. The sender to make it work is different than what I have for the idiot light, I'll guess.

[68911USA]

Here's a quick diagram. From the looks of it, the sender just reads pressure right off the engine, so there doesn't look like anything to replace "under" the pressure sender, really. Still stumped. The part in red was what I thought might need attention, but it looks like that is related to oil temperature, not pressure.

[edmayo]

Do you have the combo gauge, that is do you have numerical oil temperature and oil pressure gauges, and if so is this light near the top of the combo gauge. If yes then I think what you are seeing is the handbrake warning light. What color is the wire to the bulb holder in question, if brown/yellow that is part of the handbrake/brake pressure warning system.

[911quest]

The red part in the diagram is the Thermostat. A 68 doesn't have an oil pressure light. The two lights are the E-Brake light and the bottom is the Alt. light.

[68911USA]

Sorry if I was confusing. This is a picture (example, thanks eBay) of the gauge in the dash of the car. This is the stock, standard 911 gauge. My understanding was that there were 3 lights in this thing- a small light at 9 o'clock for the alternator, a small light at 3 o'clock for the handbrake, and the large light that takes up the bottom is a warning lamp for low oil pressure that should go out when the engine is running.

I THINK the bulb holders on the back of the gauge are different sizes for the "big light" versus the "small lights", so I think it's unlikely that I just have the bulbs pegged into the wrong holes. But uh...perhaps I should verify that...

[68911USA]

And THIS PICTURE, is an example (thanks again, eBay) of a similar gauge that I have that I was going to try to wire up IN PLACE OF the stock, standard gauge, to test the oil pressure since you can actually get a numerical reading from this one. It is stock for a 911L or S model for my year, but this is the one that I believe the sender is different, but there have been several posts about the fact that the factory connections should already be in the harness for it. I have the unfortunate situation of being absolutely, horribly color blind- and when I look at wiring diagrams it all just looks like spaghetti!

[rgrimm]

Sorry if I was confusing. This is a picture (example, thanks eBay) of the gauge in the dash of the car. This is the stock, standard 911 gauge. My understanding was that there were 3 lights in this thing- a small light at 9 o'clock for the alternator, a small light at 3 o'clock for the handbrake, and the large light that takes up the bottom is a warning lamp for low oil pressure that should go out when the engine is running.

I THINK the bulb holders on the back of the gauge are different sizes for the "big light" versus the "small lights", so I think it's unlikely that I just have the bulbs pegged into the wrong holes. But uh...perhaps I should verify that...

For the "temperature only" gauge, the 6 o'clock light should be the handbrake. 9 o'clock red is charging; 3 o'clock green is oil pressure.

[edmayo]

I believe on that first gauge you picture the large warning light at the bottom is the handbrake warning light, and the alt. light will be red and the oil press. will be green. Alt. at 9:00 and oil press at 3:00. But then again I could tell you the sky is green and how would you know? . As far as trying the combo gauge in your second picture you will need the proper sender to go with the numerical gauge. If you just want to determine oil pressure I'd suggest you go buy a generic mechanical oil pressure gauge that you can screw into the removed pressure sender hole (metric is close enough to 1/8th" pipe to work for test purposes) and then you will know for sure what you have and not have to worry about proper wiring and senders. Once you have verified pressures with test gauge then you can figure out your gauge set-up.

I'm not color blind , and they still look like spaghetti to me

[68911USA]

Thanks to both of you guys.

1. I can't believe I had it wrong about what the "big light" was for. Unbelievable. I had the "combo" gauge in my last 911, so looking at this gauge is new to me. Looks like I need to troubleshoot that handbrake warning lamp! Too funny.

2. I think I'll try that mechanical gauge oil pressure test just for fun. Thanks, Ed!

[911quest]

Here is what a correct 68 gauge would like if it had Temp & Pressure. The one with the handbrake emblem I believe is a 1970- gauge.