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Oil Pressure Wires


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I dug in to a wire loom along the top of fire firewall to rewire the electric fan, and the next time I went for a drive the oil pressure warning "O" light was illuminated. I noticed that a previously hidden wire in the loom had fallen out and made contact with the engine (grounded). When I removed the wire lead from contact with the engine, the warning light went off.

The picture shows the two sets of brown and green wires that fell out of the loom. The one with the bare connector (two brown and green wires that come together at the connector) was the one that causes the "O" light to illuminate. Does that mean that this connector needs to be hooked up to the oil pressure sender?

I disconnected the single brown wire (shown just above my index finger in the pic) and grounded it to see if that would cause the "O" warning to illuminate, and it did not. Since grounding the brown and green wire connector causes the "O" light to illuminate, do I need to connect the newly discovered brown and green wire to the sensor (I'm thinking yes but want to check with folks who know more than do I)? Any idea what the brown wire that was connected to the sender purpose may be?

Thanks

 

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No roundie 2002 I've ever seen has two wires going to the oil pressure sender switch.  This presumes, of course that you have only a warning light and not an aftermarket gauge.  You didn't say what year your car is, but if it's a squarelight, according to the factory wiring diagram, there are two brown with green tracer wires connected to the oil pressure warning switch--one goes to the warning light on the dash and the other goes to the brake fluid level switch on the brake fluid reservoir cap.  Apparently this is the power supply for both sensors. 

 

Check to see if your brake fluid warning light is functioning with this wire disconnected.  From your picture neither wire appears to be firmly attached to the terminal, so you might want to re-crimp/solder 'em back on.

 

The oil pressure sender switch has a thin metal diaphragm inside the sender.  When there's no oil pressure (or it's less than 7.5 psi), the diaphragm rests against an live electrical contact, completing a circuit and causing the oil warning light on the dash to illuminate.  When oil pressure is generated, the diaphragm distorts, moves away from the contact, thus breaking the circuit and causing  the light to go out. 

 

Hope that helps

mike

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