Oil Pressure light

So, after an agonizing week of illness, snow, and rain, I finally got my '73 out for a ride today to test out my newly functional fuel gauge, parking brake, and dash lights.

It got off to a rocky start, as I didn't warm it up enough, but once moving, she performed like a champ.

Unfortunately, my persistent electronics issues reared their ugly heads again, as my alternator light was starting to blink with the turn signals, and come on briefly at weird times. I know I have grounding issues, so I'm not worried about that for the time being.

Where I was really got worried was when the oil pressure light just blinked to life all of a sudden. It had previously been completely inoperative. So, now I'm worried that my motor is dying on me, and I hurry back home.

The car was running great, no smoke from the exhaust, no blowby, no sounds from the motor, so I am guessing that there's a problem with the sensor? Would a bad sensor cause the light to go on like that?

Thanks!

Joe

It is possible from sitting in the cold your oil has plugged the sensor hole. Remove the sending unit and verify pressure with a gauge set up (if you wish to keep your IT'S TOO LATE LIGHTS) That will tell you all you need to kow as far as getting oil.

You can check the sender with a multimeter. Engine off, meter set to resistance, disconnect the plug from the sender, measure from any good ground to the post of the sender, note the reading. Start the engine and repeat the measurement. If the resistance readings are significantly different the sender is most likely good.

Is the battery close to fully charged and does the charging voltage at the battery, with the engine running, read 13.5-14.5 VDC

Do you have an original style electro-mechanical regulator or a newer style solid state regulator (old is taller than newer)? Have you converted to higher current draw headlights (Halogen) or are you running other electrical devices that draw significant current. The older regulators sometimes are not compatible with higher current draw devices.

Does the oil pressure (rebuild the engine) light and alternator warning light problem change with the position of the dash light "dimmer" that is part of the headlight switch? The rheostat and contacts that is part of the switch can be a source of any number of dash light problems. Chuck

Chuck,

I'll answer the majority of the other questions tomorrow when I get all the fuses back in and have more time.

As for the regulator, here's a picture of it. I think the PO said it was replaced.

That appears to be a solid-state replacement regulator. Because all of the idiot lights receive +12 volts at the bulb, through the printed circuit, they are turned on when they are grounded at the oil pressure switch, temperature switch, or voltage regulator, OR if you have cracked wring that is rubbing against metal or otherwise becoming grounded. Disconnect the wire from the oil pressure switch and see if that turns the light off.

It definitely goes off when I disconnect the wire from the oil pressure switch.

What sort of gauge should I use to get an immediate test of my oil pressure? Would a compression tester work?

That appears to be a solid-state replacement regulator. Because all of the idiot lights receive +12 volts at the bulb, through the printed circuit, they are turned on when they are grounded at the oil pressure switch, temperature switch, or voltage regulator, OR if you have cracked wring that is rubbing against metal or otherwise becoming grounded. Disconnect the wire from the oil pressure switch and see if that turns the light off.

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If you have a Harbor Freight nearby, they sell cheap auto gauges that are mechanical, you could hook one up the the sender port, just to make sure you have pressure.

When I got home today, I tOok some time to reconnect everything and try out the ohm meter on the sender. Well darned if the pressure light just stopped working again. Nothing. This sort of leads me to. Believe that the sender wire is grounding out somewhere.

In my refurbishments of harnesses, I've noticed that about 35% of all gauge harness plugs (oil, temp, coil and for 72/73 idle solenoid as a fourth pin) have continuity problems. Pulling on the wires outside of the molded connector helps, but whenever I see this phenomena, I replace the plug entirely. You may well be experiencing this problem. To test it out, start the engine and have someone fiddle with the white/red wires on either side of the connector plugs. If you see the oil light go on and then off, that's your problem.

Midlife,

Thanks for the advice. What I'm going to do is get a gauge for the oil pressure and temperature. Better safe than sorry. They actually sell a "tee" where you can use the original idiot light sender AND hook up the gauge. That's where I'm going with the oil pressure light issue.

I'm also going to take your advice and work with those connectors.

As for the sender, I took my ohm meter to it while the car was off, and got infinite resistance. With the car running, I got infinite resistance. Not sure what that means, but there you go.

In my refurbishments of harnesses, I've noticed that about 35% of all gauge harness plugs (oil, temp, coil and for 72/73 idle solenoid as a fourth pin) have continuity problems. Pulling on the wires outside of the molded connector helps, but whenever I see this phenomena, I replace the plug entirely. You may well be experiencing this problem. To test it out, start the engine and have someone fiddle with the white/red wires on either side of the connector plugs. If you see the oil light go on and then off, that's your problem.

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Infinite resistance means that the unit is open, and bad.

Well, that's one easy replacement to make.

I'm still getting a mechanical gauge in there ASAP.

Infinite resistance means that the unit is open, and bad.

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Given the other issues you have been having with the wiring in the dash, and lighting, probably a good idea. Then there is no mystery as to whether you have Oil Pressure, or not. Good Luck!

I had some time last night and messed with the molded connector and determined that I do have power flowing to the oil pressure sender. I was able to ground the wire and get the light to come on (according to my 7 year old sitting in the driver's seat). No dice with the temperature light. It's not even got power flowing to the wire when I have the key in "on" position. There's power at the circuit, but I guess there's an issue with the wire as it heads out to the molded connector.

I ordered a couple of autometer gauges I'm going to be putting in there anyway, but it's nice to know that my printed circuit is at least working for the oil light. I'm going to use a "tee" so that I can run both the idiot light AND the pressure sender for the gauge. Just for originality's sake.

Given the other issues you have been having with the wiring in the dash, and lighting, probably a good idea. Then there is no mystery as to whether you have Oil Pressure, or not. Good Luck!

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If you're measuring for voltage at the temperature switch (sender) connector, the only way will get it, if the wiring is good, is if the bulb is also good. The 12 volt positive feed is on the other side of the bulb.

Tonight is the big night.

After a couple of days hanging upside down in my car working under the dash, I've got my new oil pressure gauge in, and wired up.

I now see why the PO pulled the fuse for the original, nonfunctional oil pressure sender....it was stripped, and they didn't want to deal with changing it. I couldn't get the socket to fit it to get it off. What I ended up doing was putting a 24mm socket on it and then hammering it down to get it to catch. After that I was able to get it out.

The new sender is about 3 times as big as the old one. It's an Autometer electric gauge (1.5")....what I did was wrap the threads in the yellow pipe tape and threaded it in by hand. As I can't get a wrench on it to tighten, I just did it as tight as I could by hand, and I'm hoping that will work.