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Discussion Starter #1
Some of you may remember my threads about oil pressure. Well... I never noticed this until recently, but when I turn the car to "ON" with out actually starting the car; the oil pressure gauge moves to near high. Now this cant be normal. The engine isn't even on. There should be no oil pressure. What's up with that?

I just replaced the oil pressure sender, and for all I know the gauge works fine.
 

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The current to the switch is being electrically pegged, the pressure switch is not really sensing pressure.
 

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Every classic Mustang I've owned has done that, I wouldn't worry about it unless it doesn't normalize after the car is started. I believe it is the instrument voltage regulator that hangs a little upon startup. The IVR uses bi-metal contacts that switch off and on at a specific rate to regulate voltage to the instruments. I think the contacts need to heat up a little before they start working properly.

Just my theory and $.02
 

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Discussion Starter #5
It doesn't normalize...

I ended up throwing a mechanical oil pressure gauge on a few weeks ago just to see if my oil pressure was really messed up.
 

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What year car do you have?

Does it just do this on the oil pressure gauge? If so you may have a bad sender, wire, or gauge.

The oil pressure, fuel, and temp. gauges are all identical internally (at least 65-66 & 67-68) so you should be able to move the sender wire from the oil pressure gauge to the temp or fuel gauge and determine if it is the gauge, wire, or the sender.
 

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Discussion Starter #7
1966

Yes, only the oil pressure gauge. The sender was just replaced about 2 weeks ago, and a new wiring harness about 2 months ago.

I tried wiring the oil pressue gauge to the water temp sender and the gauge works fine too. So its not the sender, wire, or gauge. That I'm aware of.

*edit* it could be the gauge. I would have to test it again when the engine is cool.
 

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you have the sender for the light; you need the one for the guage

the light sender conducts fully with no oil press, the guage sender conducts more as oil pressure increases

the guage sender is MUCH larger and looks kinda like a bell
 

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When you wired it to the water temp sender and you say the gauge worked fine then I would have to point to the oil pressure sender, even though you already replaced it. If you pull the wire off or the oil pressure sender (make sure it doesn't get grounded), does it drop to L? If so it is the sender, if not it is the wire. I know you've replaced these items already, but sh!t happens /forums/images/icons/smile.gif

Good luck.
 

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I just saw your edit. You can test the gauge (hot or not) by pulling the wire from the sender. If the sender wire is off the sender and not grounded your gauge should read L, if you ground the sender wire you gauge should read H. If this works your gauge and wire are good. If this doesn't work you need to pull the wire off of the gauge and check it for a short to ground, if that is good than it is the gauge.
 

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Discussion Starter #12
I did your test... read L when I took the wire off the sender and H when I grounded the wire.

So it must be the oil pressure sender then. Arg, I just bought it.
 
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