Oil pressure light

Pflyer

Pflyer

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My 1974 e9 oil light won’t come on when the ignition is turned on. I’ve ordered a new pressure switch from Amazon and will install. Other than the bulb being burned out, does anyone have any ideas if that’s not it?
 
Pflyer said:
My 1974 e9 oil light won’t come on when the ignition is turned on. I’ve ordered a new pressure switch from Amazon and will install. Other than the bulb being burned out, does anyone have any ideas if that’s not it?
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The bulb. If it is OFF with ignition on but not starting the car, then it is the bulb, not the pressure switch. If it is ON but turns OFF after starting then it may be the pressure switch or the wire to it. I think that grounding that wire closes the circuit and it should be ON.
 
Arde said:
I think that grounding that wire closes the circuit and it should be ON.
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... which makes it easy to determine whether the problem is the bulb or the sender: just pull the connector off the sender while the ignition is on and touch it to ground while a helper monitors the bulb. If it glows, the bulb is good and sender bad. If it doesn't glow, the bulb (or socket, or wiring) is bad and the sender's condition is unknown (but probably OK).
 
To allay fears of "do I have oil pressure", put a test light between power and the switch contact with engine off - it should turn on.
Then while still connected and lit start car - should then go off as soon as pressure builds up.
That's basically what the dash indicator does.
 
Thanks all. I will test the wire on ground to see if it’s the bulb. I believe my mechanic changed all the bulbs when he had the dash out. Could be a defective bulb or a short to the bulb.
 
Short to the bulb would cause the bulb to light up, or blow a fuse. Circuit provides power to the bulb, with the sensor acting as a ground. If there were a short before the bulb, this would blow a fuse. After the bulb and the bulb would glow.

This is why Jay Makro suggests you can ground the wire to the sensor to determine if the bulb is good.
 
I grounded the wire and the light came on. Lo and behold, when I plugged the wire back to the sensor, the light stayed on. Bad contact. I’ll steel wool the nipple to clean it. Thanks again all!
 
Another problem solved before breakfast. We are awesome, the only thing we cannot fix is rust.
 
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Pflyer said:
I grounded the wire and the light came on. Lo and behold, when I plugged the wire back to the sensor, the light stayed on. Bad contact. I’ll steel wool the nipple to clean it.
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OK, glad to hear that you are making progress and don't have to crawl behind the dash to change the bulb. However, steel wooling the contacts isn't going to do anything; that'll just make the light shine brighter. It sounds like your sensor is permanently showing low oil pressure (e.g., grounding the wire) and replacing the sensor is the solution for that.

But I'm still puzzled: isn't this the same sensor that previously didn't light the bulb under any circumstances? And now it lights it whenever the key is on, whether the engine is running or not? What has changed?
 
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I read the update as the lights stays on while the ignition is on, but I assume it goes OFF once you start the engine.
 
Arde said:
I read the update as the lights stays on while the ignition is on, but I assume it goes OFF once you start the engine.
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Hmm. If that's what Pflyer meant, then steel wooling his nipple makes a little more sense. Squeezing down the female connector on the wire to tighten the connection might help as well.
 
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