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Discussion Starter · #1 ·
Hello,

I recently took down my gas tank to replace it and while i was at it i want to fix the gas gauge. currently it reads at 5/8 full when the float is all the way up. ive tested the sending unit ant it reads exactly at the specs 0=E 95=F OHMs. Ive tested the wire from the tank to the firewall and the ground is good also. when i read the circuit between the ground and the lead to the sending unit i get 68 OHMs. where should i go checking next? Is this a short in the wire? also would the 68 OHMs give me the faulty gas gauge reading?
 

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Yes. The 68 OHM reading should be zero ,or close to zero.Repair that part of the circuit
 

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fuel reading

yes that drop in ohm's will give u false reading as u've found. now u need to MAKE sure u have a good ground on tank. even if u run a new wire from tk to ground. u may have bad wire from tk to firewall. that wire is most likely around a 16ga. u can just get around 10' of it and measure the ohms so u have a good idea what your looking for.. it should be very close to a short.
 

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Replace the wire end crimp connectors, corrosion between the wire and connector is most likely causing the resistance.
 

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Discussion Starter · #5 ·
Thanks for the suggestions! Ive already replaced the ground to tank, and the connector to the tank is in GREAT shape. The wire from firewall to tank connector reads 0 OHM. So now i think i need to investigate the actual gauge, or the connections from the firewall to the insturment panel circuit board. Any suggestions on how to conduct these tests? Especially how to test the fuel gauge?

And a side note, how do i test the temperature gague for propper function also?
 

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sending units

one way to test fuel is have a helper. u need to know the height of tank so u know swing. key on and have helper move float up and down kinda slow. . with temp, ground the wire to the sender and gage will move full scale so u know gage is working.
 

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Here is the answer, the gauge you have, does not match the sending unit. I believe the sending unit you're using is one you cobbled together.
Getting a gauge to match what you have might be the quickest way to solve the problem

Or


Love the gauge my first choice, cause it is a match with the others........?

Change out the sending unit....... no matter what you decide, the two components MUST match

95 ohms says the sending unit is GM



Cheers,
Greg
 

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As you have mention the temp gauge as well and not knowing what vehicle this is on there is a chance that there is a voltage regulator on the back in the instrument panel that is faulty. This is what you are looking for. It is about 1/2" long. These regulate the fuel and temp gauge on some cars. Might also be called a Instrument Voltage Stabiliser ( IVS ).

http://www.hotrodders.com/forum/attachment.php?attachmentid=382857&stc=1&d=1508166803some
 

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Discussion Starter · #11 ·
So i tested the ground by wiring it direct to a known ground, that made no difference. Is there a way that i can test the gauge by itself? Using a battery connection to each lead on the gauge?
 

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On a GM

If you remove the gauge and looking at the rear, there should be a resistor pack, bolted to three terminals forming a “V” shape. The upper left terminal is the sending unit wire, Tan on GM. The upper right is the switched 12v supply. The bottom center is the gauge’s ground.

Needle pegs full or past full – Break in the fuel sender wire (Tan) or tank’s ground wire is disconnected…. To test the gauge….. disconnect the tan wire the needle should peg full.... (ground the tan wire and the needle should peg empty)

Needle pegs empty or past empty – Break in the Gauge’s ground connection (under the dash) (regardless if the tan wire is disconnected)

Needle’s stuck in one place – Break in the Gauge’s 12v supply

Needle only moves to ¼ full – The resistor on the rear of the gauge is bad or has ground out to the side of the gauge housing.
 
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