Old 08-21-2019, 03:54 PM
Red Box Rebel Red Box Rebel is offline
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Join Date: Jun 2005
Location: Republic of Texas, San Antonio
Posts: 247

Okay, the tank was removed and repainted, The new sending unit was installed and the tank was reinstalled with new attaching hardware.

The wires have all been re-attached and the fuel gauge works as good as new. A big Thanks to everyone that provided tips and advice.

Old 03-22-2021, 11:27 AM
CLEL01 CLEL01 is offline
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Join Date: Jul 2007
Location: Indiana
Posts: 21

Thanks for your input to the Forum. Help please with fuel gage pegged on F. '64 GTO. What next steps?

Using volt ohm meter:
1. Key on, 11v on tan wire unplugged and grounded to ground point near tank
As above, gage needle is past F. Switching key off needle moves down from peg slightly and back to peg switch on
2. Key on sending unit terminal grounded and needle pegs F
3. Sending unit terminal to ground 74 ohm. Tank is down a little from full
4. Unplugged tan wire to ground 45 ohm.

I have spare gage pn 6430125 I think is 1965 so 90 ohm. Across the wire wound resistor between the two blades 40 ohm. Left blade to ground stud 90 ohm. Right blade to ground 130 ohm.

Old 03-22-2021, 12:31 PM
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Peter Serio Peter Serio is offline
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Join Date: Mar 2000
Location: Columbus, OH 43209 USA
Posts: 2,555

What year gauge is in the car right now, a 64, zero to 31 Ohms (range span) or a 65 gauge (zero to 90) ohms range span? Did you test the sender before you put it in the tank? ALL senders should be tested prior to install, it is almost certain that the makers of new reproduction parts do not bother to test their senders prior to shipping.

Your test #1 does not seem right to me. Could you post photos of the front at the back of the gauge? Also that gauge needs ground at the silver steel plate which is the access hatch at the back of the gauge. Without a "reference ground" at the dash the gauge will never work!!!

I would like to see how this is wired. Any GM dash gauge for Fuel, temp or oil pressure absorbs voltage so the input voltage (measured) would be at least 11 volts; more in the range of 12 or 13 if the engine is running but the output voltage from the tan wire back to the sender would be no more 3 or 3.5 volts. Especially with a fuel gauge; you would NEVER EVER run 11 volts into a fuel tank sender. A) that could burn the resistor card & damage the sender and B) If that were to ever spark across the resistor card via the copper touch tab and there was almost no fuel in the tank the resulting spark could very well ignite the vapors inside of that tank, which would be VERY BAD !!!

Peter Serio
Owner, Precision Pontiac
Old 03-23-2021, 07:48 AM
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Greg Reid Greg Reid is offline
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Join Date: May 2003
Location: Palmetto, GA. USA
Posts: 14,778

There's the guy that can answer all your questions way better than I can ^^^

Greg Reid
Palmetto, Georgia

Old 03-23-2021, 03:27 PM
CLEL01 CLEL01 is offline
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Join Date: Jul 2007
Location: Indiana
Posts: 21

I disconnected the rear harness to take the sending unit out of circuit.
Switch on, I have 12 v to ground on tan wire at the fuse box side of harness connector.

Pulled dash forward enough to access fuel gage. Compared what I saw to photo of gage connections. Homer Simpson "Doh!" Reversed leads to correct terminals and gage reads correctly now.

Thanks for your comments.

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Old 03-27-2021, 06:24 PM
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LATECH LATECH is offline
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Location: Indoors
Posts: 583



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