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I have a new (to me) 1978 Spider that I am sorting out. The PO had the engine rebuilt, and she seems to run very well now that I replaced the tank fuel pump.

I have a very basic electrical question.

Problem: The oil light is always on and the oil gauge is either on or off, with no measurements in between. So as soon as the motor is running, it jumps to about 100 and does not move a bit, whether at idle or revved up. It is just binary - on or off.

My Theory: I am wondering if the the oil light and oil gauge wires could be reversed. The sensor on the left of the engine, by the alternator (which I believe is the oil gauge sensor) has a gray wire plugged into it. (My wiring diagram suggests gray wire is for the oil light's)

Likewise, the wire on the sensor on the right of the engine (light sensor?) has a red/black wire (gauge sensor?).

Questions: So if I have my wires and sensors straight, they seem to be crossed, right? Shouldn't the gray wire be on the right sensor - and the red/blank on the left?

And if I swap them "back" and I am wrong about this, could it damage the gauge or anything like that? I am guessing not, but I am not great with electrical stuff and do not want to make problems worse by damaging anything.

Thanks all!
Cervantes
 

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I am wondering if the the oil light and oil gauge wires could be reversed. The sensor on the left of the engine, by the alternator (which I believe is the oil gauge sensor) has a gray wire plugged into it. (My wiring diagram suggests gray wire is for the oil light's)
The wires could be reversed. But they are probably reversed behind the dash - not underhood. The sensor near the alternator is for the light, so the grey wire is connected correctly. The sensor for the gauge is on the right side of the engine.

if I swap them "back" and I am wrong about this, could it damage the gauge or anything like that? I am guessing not
No, you won't damage anything. Heck, they're probably mis-wired already! Start by just unplugging one (the light sensor on the left side of the engine is the easiest to access) and see what happens. If the gauge's behavior changes, you will have learned something.
 

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Make sure that the sensors have not been switched. The pressure switch, on the exhaust side is the small sensor and the Gauge sensor, on the intake side is the big one.
If you disconnect the grey wire from the sensor and ground it, the oil warning light should come on.
 

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Discussion Starter #5
thanks for the ideas!

Thanks all! I should have a few minutes tomorrow to take a closer look. I strongly disputed the reversed wires at the dash or the sensors being reversed on the block.

I will keep you posted.

Cervantes
 

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I strongly disputed the reversed wires at the dash or the sensors being reversed on the block.
Sheesh. I mean strongly "SUSPECT" the reverse wires... not "disputed!" Auto correct does some strange things.

OK, I checked the sensors. Exhaust side is smaller, so that looks correct. BUT...

...I checked the wires to the various "idiot lights" at the dash, as suggested. Oil Sensor has a blue/white wire! That wire should be the Fuel Pressure light. Unplugged the wire from the fuel sensor, Viola! My "oil" light went out. They had been switched!

So I checked what wires were in the Fuel Pressure light. Two pinks.Oh, and I found the gray wire (fuel light) not connected to anything!

So I will pull out the wiring diagram and get that all sorted. I suspect a similar issue on the oil gauge.

Based on now knowing the Fuel Pressure light is on, it looks like I also need to replace my engine-bay oil filter and if that does not work, main fuel pump.

Thanks for the suggestions. You all pointed me in the right direction. Now I just need to sort the wires. I think that should be simple enough, though tedious. Hmm... Are these small bulbs a standard item I can get at NAPA, or are they a strange special order light bulb. I wonder if they could be replaced with an LED... Hmm.

Thanks for all the help. I am sure I will have a hundred other simple problems that I may need help with. Thanks for your patience.

Cervantes.
 
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