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Join Date: Sep 2005
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Oil level needle is pegged

I have pulled the wires at the sending unit and put a test light on them; the light does not come on. The guage stays pegged even with the wires at the sending unit disconnected.

I have not pulled the guage itself, but it is obviously receiving a current, or it would not peg when the ignition comes on.

What is the most likely cause? A short? If so, where?

(There is a VERY old thread on this subject, so I apologize for the new one, but the old one did not help.)

Old 10-18-2005, 06:06 AM
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Start by pulling the gauge out and inspecting the wires leading to it. Sounds like the insulation is cracked on one and shorting.
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Old 10-18-2005, 07:18 AM
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I do believe there is a short to ground in the wire somewhere. Could be bare anywhere but you may want to check in the area of the tank. Didnt the targa do that Harold? I recall that it quit working and I could move the wire around at the tank and it would move erratically.
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Old 10-18-2005, 07:20 AM
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Also, to get the gauge O-Ring to seat properly on installation lube it with glass cleaner (Glass Plus, etc.).
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Old 10-18-2005, 07:21 AM
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My oil level gauge works the same way. If I disconnect the wire to the sender the gauge pegs high. When I reconnect the sender wires, the gauge reads right again.
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Old 10-18-2005, 08:15 AM
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Bad sending unit or disconnected wire = pegged gauge. Check continuity of the wire between the sending unit and the rear of the gauge, but the problem is very well a bad sending unit.
Good luck -
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Old 10-18-2005, 08:51 AM
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Sounds like a grounding issue to me.
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Old 10-18-2005, 09:50 AM
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My oil level gauge did this. I removed the sender cleaned the contacts and replace the connectors, didn't work any better. I replaced the oil level sender and it works great now
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Old 10-18-2005, 10:34 AM
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Thanks guys

Since you have confirmed that a bad sending unit will peg the guage, this is probably the issue.

Thanks for your help!
Old 10-18-2005, 12:58 PM
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The oil quantity sending unit in my 78 is a pretty darn simple device - just a float arm on a wire-wound rheostat. If yours is this same type, anyone handy with basic electonics can repair them.

Clean, inspect wire windings on the insulator, check the slider contact and the tension. That's about it.

Definately inspect it before deciding to plunk down $80 on a new one.
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Old 10-18-2005, 01:10 PM
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Check continuity from the oil level sender to the gauge(I think a green wire with white stripe), you should also have continuity from the other wire to ground. Also ohm across the two sender terminals - it should not be infinity... good luck
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Last edited by Bill in OKC; 10-18-2005 at 01:35 PM..
Old 10-18-2005, 01:31 PM
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Maybe there's 24 quarts of oil in the engine?
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Old 10-18-2005, 01:34 PM
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Okay...What in the heck does "pegged" mean? The neddle is stuck somewhere? Doesn't work at all?

My oil level gauge stopped working. Was the neddle pegged? I replaced the sender unit. Now it is working. Is the neddle "unpegged" now?

My apologies for the newbie question.
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Old 10-18-2005, 05:32 PM
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pegged means needle all the way at the top indicating 'super full'..
ryan
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Old 10-18-2005, 06:17 PM
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Pegged means it goes to the maximum deflection. Gauges have a small "peg" there so the needle must stop and not make a complete circle and twist off. The oil level sender has a ground on one side and the other wire/side goes to the gauge. The sender is a variable resistor. that changes based on the movement of a float mounted on a lever arm floating in the oil. You can tell the side attached to ground by simply looking. An "open" will give you full needle deflection (pegged) and a short (to ground) should give no needle deflection. You can test the sender by disconnecting the output wire going to the gauge. That creates an "open" which gives full deflection. Touching that wire to chassis ground should give no needled deflection. If it works like described...the problem is either the sender or bad contacts on the ground wire side. If it does not, the problem is in the gauge or wiring between the sender and gauge.
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Old 10-18-2005, 06:25 PM
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Do you have to drain out all the oil when removing the sender??
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Old 10-18-2005, 11:36 PM
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Probably not Pål since the sender ain't located in the bottom..
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Old 10-19-2005, 12:00 AM
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Quote:
Originally posted by Kroggers
Do you have to drain out all the oil when removing the sender??
No, but you would need to be very careful not to knock wheelwell dirt or gasket material into the tank. So clean it up good first and/or change oil afterward.
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Old 10-19-2005, 12:07 AM
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bigchillcar and fintstone--thank you for explaining "pegged." I love this board. The depth of knowledge is mind boggling.

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Old 10-19-2005, 03:00 AM
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