Gas Gauge not working correctly

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Soonersace
Posts: 46
Joined: Mon Dec 02, 2013 8:15 pm
Location: Minnesota

Gas Gauge not working correctly

Post by Soonersace »

I just got a new gas tank. I had my local garage replace the float and sender and all that.

I do have a 55 that has a 12V conversion.

The car ran out of gas despite showing half a tank.

Does anyone know how to adjust the gas gauge to show lower?
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55Greg&Amy
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Re: Gas Gauge not working correctly

Post by 55Greg&Amy »

You have to remove the sending unit in the tank and bend the float arm
Greg Minnich
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paul2748
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Re: Gas Gauge not working correctly

Post by paul2748 »

Does the gas gauge seem to stay a long time on full? The bending the arm on the float my fix it.

Might try this - pull the sender, keeping the wire attached. Run a temporary ground from the sender to a good ground on the car. Manually work the arm up and down (slowly) to see if you get the full range on the gauge. If so, bending the arm should work. It might be better if the tank only has a gallon or two to adjust the arm - the gauge should read empty with a gallon or two left in the tank. Make sure the car is fairly level when adjusting the arm.

I would not run the temporary ground to the tank because it is now open and fumes are escaping ( possible spark).
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CSavaglio
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Re: Gas Gauge not working correctly

Post by CSavaglio »

Being that it's a 55 converted to 12v, I would make sure the correct sender was used. If your gauge was swapped with a 12v 56 version, you'd need a corresponding sender. If it was left as the original and a voltage drop was used, a 6v 55 sender should have been used. Mixing different voltage gauges and senders would give incorrect gauge readouts. The shop may have put a generic 12v unit in figuring the car is 12v but it would need a correct 6v tbird sender if the original gauge is in the dash.

If all is matched properly, bending the arm can be done to calibrate. Paul's advice about pulling the sender to test with a temp ground is good and I would add to do it in a well ventilated place and maybe put some tape over the sender mounting hole to limit the flammable fumes some.
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Florida_Phil
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Re: Gas Gauge not working correctly

Post by Florida_Phil »

My 1955 TBird was converted to 12 volts when I bought it. The gas gauge never worked right. The original 6 volt fuel gauge is not compatible with the new resistance type sending units. I recently replaced my gas tank as well. I purchased a special 12 volt conversion gauge and sending unit kit from Casco that fixed the problem. It's a little pricey, but it works.
apines
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Re: Gas Gauge not working correctly

Post by apines »

The sender and gauge have to match each other and match the battery voltage and between differences in model years and '55 conversions from 6V to 12V there are a lot of permutations. I'm pretty sure this is comprehensive (resistance ranges are according to CASCO so maybe not definitive):
'55 (original 6V): uses a 6V gauge, 20Ω to 90Ω sender (9275A)
'56: uses a 12V gauge, 100Ω to 300Ω sender (9275B)
'57: uses a 6V gauge with a regulator, 10Ω to 80Ω sender (9275C)
So your choices on a '55 converted to 12V are:
1) original gauge and sender, add a 6V regulator to the gauge (this takes care of the temp gauge, too)
2) replace both with 12V parts for a '56
3) replace both with 6V parts for a '57 and add a 6V regulator to the gauge
4) replace just the sender with one for a '57 since it's pretty close and add a 6V regulator to the gauge (won't be quite as accurate since the resistance range is a bit different)

Options 1 and 2 seem like the most realistic, I can't see why anyone would have done 3 or 4. Without the regulator the fuel and temp gauges on a 12V-converted '55 will read really high.
current:
1966 Ford Thunderbird Q-code convertible with Highway Pilot
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1955 Ford Thunderbird
1974 Triumph TR6
1968 Ford Galaxie convertible
1974 VW Super Beetle
1981 Checker Marathon
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