Oil light backwards
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Oil light backwards
I have a rust free '78 F100 351W.
I updated my 302 a few years back. I've owned it for over 25 years.
My oil pressure light is backwards.
The light does not come on until the engine is running.
I've changed the sending unit. The motor is grounded well to the frame and cab. Any thoughts on what the issue might be?
Tia Rob
I updated my 302 a few years back. I've owned it for over 25 years.
My oil pressure light is backwards.
The light does not come on until the engine is running.
I've changed the sending unit. The motor is grounded well to the frame and cab. Any thoughts on what the issue might be?
Tia Rob
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Joined: Jan 2001
Posts: 56,984
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From: Virginia
Verify something for us. Take a ohmmeter and put it on rx1 scale. With the engine off, unplug the wire from the sending unit and take a ohm reading between the sending unit terminal and a good clean metal spot on the engine. Then start the engine up and do the same thing again. What readings do you get both times?
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Joined: Jan 2001
Posts: 56,984
Likes: 2,738
From: Virginia
Something is wrong with that sending unit. If you have a oil light, you should have a little guy with one stud coming out, not a big fat can looking thing. The little one is a switch which is what you want, it should read zero ohms to the engine metal with the engine off. This will light the light when the key is turned on. The wire going to the sending unit is actually the ground for the light. When the switch see's anything above 5lbs pressure, it ungrounds the wire and turns the light off.
That 63 reading is suspicious, I am wondering if you have the gauge sending unit instead of the switch you need for the light. The sending unit for the gauge will read a continuos variable ohms to ground that moves the needle back and forth up and down the scale on the gauge.
That 63 reading is suspicious, I am wondering if you have the gauge sending unit instead of the switch you need for the light. The sending unit for the gauge will read a continuos variable ohms to ground that moves the needle back and forth up and down the scale on the gauge.
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