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Testing the fuel gauge
#11
great thanks for all the info. guess I'll have to get under the dash to figure this out. I'll have to find the time to do it. But I will post here as soon as I do.

Once again thanks and a couple of rep points have been sent your way.

Eric


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DRIVE IT DON'T STORE IT!
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#12
There is a 5 volt pulsating DC from the instrument cluster going from the gauge to the tank. The float in the tank varies a resistance that changes the current to the gauge. When the tank is at low level the resistance at the sender is high and gives you a low level reading. When the tank is full there is little resistance (just like a dead short to ground) and the level will read high on the gauge. If you are reading E that tells me you either have a gauge that that has a bad bi-metallic strip or you have 2 wires making contact in your harness. Odds are it's the gauge, but wires are easier to repair and get to vs taking your gauge cluster out. So we troubleshoot hoping for the simpler solution first.

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Just cruising along minding our own business when BAM!!! The LAWS show up.
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#13
There is a connector in the trunk, left side you can try the ground/10 ohm resistor from there. If it moves the gauge upscale toward full you'll know it is the wire to the sender, connector at sender, sender, or the ground that should be screwed to the trunk latch support. Good Luck, Chuck
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#14
Excellant idea, since he's getting the voltage that will tell if it's gauge or sender. If it stays at E with the resistor the strip in the gauge is gone. Quality thumb

[Image: 2rr7aiv.png]

Just cruising along minding our own business when BAM!!! The LAWS show up.
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#15
One other thing to consider....because it happened to me. The float came off the arm that moves the resistor arm, thus it showed empty at all times, while there was some resistance measured on the sender, and I had proper voltage from the instrument cluster, and no loss of ground.

DOH~

1972 H-code Mach1
2010 GT Premium
2015 Hyundai Sonata Sport 2.0T
1995 F150- The "home depot" machine
2012 Harley Davidson Road Glide Ultra
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#16
Resurrecting this thread while I chase similar demons.

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"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#17
(12-29-2011, 06:18 PM)trainey Wrote: One other thing to consider....because it happened to me. The float came off the arm that moves the resistor arm, thus it showed empty at all times, while there was some resistance measured on the sender, and I had proper voltage from the instrument cluster, and no loss of ground.

DOH~

My '73 shows empty all the time, too.  Considering that my gauge stopped working immediately after I put a new fuel tank in, I would think this is the first thing I should check.  It'd be amazingly coincidental that a problem occurred elsewhere along the line right at that moment.
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#18
My float is attached. Everything looks kosher.

Is it possible for the enclosed resistor in the sending unit to be kaput? Is there a way to test it when it's on the bench (doesn't appear so, but what do I know)? Could it have died just from removal or installation (I was pretty gentle and didn't bang it around).

At any rate, I'm gonna put it back together and do some of the electrical tests mentioned in this thread. If anyone has any info regarding the enclosed resistor, please let me know.
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#19
Did you add a bend in the float rod? Most of the time it needs to be bent a little. I would probably test the float with the key on, have the arm fully extended, and check gauge, then lift the arm on the float to the top and see if the needle moves to full. If the gauge goes up, then add about 5 gallons of fuel in the tank, put a slight bend in the float arm, then see if you are near a 1/4 tank.
I will be going through this same thing in the next few months, let us know how it goes. Good luck

Tom
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#20
(02-23-2019, 06:08 PM)vintageman Wrote: Did you add a bend in the float rod? Most of the time it needs to be bent a little. I would probably test the float with the key on, have the arm fully extended, and check gauge, then lift the arm on the float to the top and see if the needle moves to full. If the gauge goes up, then add about 5 gallons of fuel in the tank, put a slight bend in the float arm, then see if you are near a 1/4 tank.
I will be going through this same thing in the next few months, let us know how it goes. Good luck

Tom

I didn't think to check it outside the tank, plugged in, and key on while moving the rod. 

Thanks, I will do that tomorrow.
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