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oil pressure light wiring?


wex65

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Hoping someone can help.

Our recently acquired 55 has no oil pressure light. I found this light hanging behind the dash, I don't know if this is it?

When the ignition is turned on the bulb lights but stays lit when the engine starts. If I had to guess, I suspect this IS the light but maybe a sender unit or wiring issue that causes it to remain lit?

I cannot for the life of me locate where it plugs in behind the dash. The fact that I am 6' 2" and 220 pounds doesnt really help either! I can barely get my head under the dash and even then can see very little even with a little mirror on a telescoping arm. I can locate a bulb already in place behind what looks to be behind the the oil pressure bulb...but that appears to be a night light that lights the speedo area of the instrument panel.

Can anyone confirm whether the bulb IS the oil pressure bulb? wires are black/green and white/red. If so is the hoel into which it should go accessible from underneath the dash?

*IF* this is the case I suspect I next need to go looking for a sender unit.

Any help appreciated.

I thought the image below was attached in TINY format but clicking on it makes it far larger.

post-85740-143142628716_thumb.jpg

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My 55 manual shows W-R, white/red tracer from the bulb to the sender

B-G, black/green tracer, as the power supply. This also powers other gauges, so its kind of a loop.

best of my recollection, the odd, long body socket is only used on the oil and gen lights.

I've got a small, led light on a flex stalk. With a helper, shine the light thru the back, they should see the oil light lens glow. If the lens glows otherwise, someone crossed the bulbs. But your comment on finding it rings a dim bell that it is difficult to find. As a last resort, get under the dash in the dark, and try a flashlight thru from the front, an see if the lights visible underneath. I share your pain about trying to get under the dash, and I'm only 5-11.

grounding the sender connection, key on, should light the lamp. I'm pretty sure pressure opens the sw.

disconnect the battery while you're under there. The ignition and light sw always have a hot lead and dropping or bumping something will be a straight short to ground, and can smoke most of the harness. There might also be hot connections on a couple circuit breakers behind the dash for power windows/seats.

unless your car has been rewired, you might also find the wiring is brittle, and the insulation breaks easily. If so, you might want to look at replacing the wiring either with stock harnesses, or a modern fuse panel with a wiring kit. Depends on where you're going with the car. A buddy started an OT 56, and the ignition sw failed to ground. He smelled the smoke, and got the battery disconnect off before the fire started, but the whole main harness melted, fusing not only the insulation, but also the copper. Lots of energy in a charged battery.

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...grounding the sender connection, key on, should light the lamp. I'm pretty sure pressure opens the sw.

Thanks a million. The torch method worked a charm!

Well, I got the light in the hole but I went to ground the sender wire and before doing so measured full battery voltage on it. Surely grounding that will blow something, shorting 12v to ground??

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You should have full measured voltage, and the resistance in the meter doesn't flow enough current to light the lamp.

when in doubt, I use an inline fuse holder with a 5 amp fuse. It should allow the lamp to light, but if there is a fault, the fuse goes before any damage is done. Kind of a fail safe test lead. If that lights the lamp, then you know the sender is bad. If not, or the fuse blows, keep looking.

i note you said 12 volt. Has you car been converted form the original 6v positive ground? Not that it affects the discussion.

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You should have full measured voltage, and the resistance in the meter doesn't flow enough current to light the lamp.

when in doubt, I use an inline fuse holder with a 5 amp fuse. It should allow the lamp to light, but if there is a fault, the fuse goes before any damage is done. Kind of a fail safe test lead. If that lights the lamp, then you know the sender is bad. If not, or the fuse blows, keep looking.

i note you said 12 volt. Has you car been converted form the original 6v positive ground? Not that it affects the discussion.

Mike, I kinda had a brainwave earlier and realized the voltage was fine. I connected the sender unit to ground and the light lit so it looks like I just need a new sender unit.

Yes, the car was switched to 12v -ve earth by the PO.

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  • 3 weeks later...
Guest skygazer

Since I just re-inserted the "oil" light on my 55 last weekend, I feel qualified to comment. It can be reached from under the dash, but not readily. Lying on my back, I had to have my head all the way forward in the footwell, and I could just get a glimpse of the hole above the steering column bracket. Once I knew where to guide the lamp, I was able to position it by feel and get it to snap back into position.

Getting under the dash is a pain, but it is a valuable skill to learn. I've learned to start by leaning over the driver's doorsill facing forward, aiming my right shoulder at the floor, doing a limbo under the steering wheel, and ducking my head to miss banging it on the shifter. This is easer when the seat is out, but not a lot.

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