55 Ford fuel gauge issue

['46Ford]

55 Ford, Fairlane, 272, converted to 12V system. The fuel gauge on the dash will not read properly. Goes to full when tank is full, the needle will fluctuate down and up when driving, going from full to half or quarter then back to full. I've put in a new tank, sending unit, checked wiring going from tank to gauge, not grounding anywhere. Is the 12V conversion an issue with the gauge. The needle on the gauge jumps a little when going up from empty when I first turn the ignition on. Any insight on the issue is appreciated. Thanks in advance.

[fordrodsteven]

Originally Posted by '46Ford

55 Ford, Fairlane, 272, converted to 12V system. The fuel gauge on the dash will not read properly. Goes to full when tank is full, the needle will fluctuate down and up when driving, going from full to half or quarter then back to full. I've put in a new tank, sending unit, checked wiring going from tank to gauge, not grounding anywhere. Is the 12V conversion an issue with the gauge. The needle on the gauge jumps a little when going up from empty when I first turn the ignition on. Any insight on the issue is appreciated. Thanks in advance.

Hill's Thunderbird lists a dropping resistor for when 55's Birds are changed over to 12V . P/N 9280-DR for $29.95. I have also seen at the H.A.M.B. where someone talking about Ford fuel gages said they were 6V up into the 1980's. Do you have an instrument voltage regulator (also called the resistor) in your wiring circuit? You can also try P/N 10804 at a regular supply house.

Hill's catalog also has a note that says "55 fuel gauge has 11-12 OHMS resistance. 56 has 38-40 OHMS resistance and 57 has 13-14 OHM resistance. Measured from terminal to terminal."

[Dobie Gillis]

You need a CRV (cluster voltage regulator) if you don't have one. It drops the voltage to the gauges to 6v. Feeding 12v to 6v gauges will fry the gauges. Are the oil pressure and temp gauges acting up, too? If your fuel sender is one of the universal ones it will never work correctly with the original gauge. Modern gauges work on average resistance, old Ford gauges work on average voltage, different principles.

['46Ford]

I do have a resister that will drop the voltage back to 6V Guess I will try that.
The gauge is original. On the oil, generator and temp, the car has after market gauges mounted under the dash, they work fine. The sending unit was sent with the new gas tank, supposed to be correct for the original '55 gauges.
Hope the gauge isn't 'fried' Do you know of aftermarket gauges that would work on this set-up. Thanks.

[dmsfrr]

Originally Posted by '46Ford

. . .
Hope the gauge isn't 'fried' Do you know of aftermarket gauges that would work on this set-up. Thanks.

If the oem gauge works at all it isn't fried, there's only one circuit thru it. Is there dirt inside it?
Dobie is correct about an oem fuel gauge when connected to a newer sender, they don't use the electrical signal the same way. The original setup used current flow / heat to move the needle.

The T-Bird resto houses sell a reproduction fuel gauge that should be able to read the newer sender.
.

[rotorwrench]

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The older 6-volt cars had the King Seeley systems that were a current pulse system. They are not reproduced. The reproductions are all resistance type senders and most are not calibrated with the prober Ohms resistance for the original KS indicator units. They can be made to function but seldom do they function well with the repro sending units. If a modern type replacement gauge is available as was previously mentioned, that would be a good route to go. KS senders can usually be repaired but many of the replacement fuel tanks don't have the correct bung to fit them.


The modern Runtz IVR type voltage drop is the most reliable. The old CVRs (constant voltage regulator)are current pulse type units that seldom hold the voltage at proper level. The circuit is constantly opening & closing so the voltage fluctuates a lot. 5th Avenue Internet Garage has the Runtz converters. A person can make their own but it's easier to buy the one from Randy Rundle.

[Rusty_S85]

In 55, they were 6 volt if you convert to 12 volt you need one of those 6 volt, voltage reducers attached to your power feed for your gauge cluster. this will drop the voltage at your sending units down to 6 volts as well.

In 56, they were 12 volt with no voltage reducer, my understanding is 56 was the only year ford ever ran a full 12 volts at the gauges themselves and in 57 they went to voltage regulators that pulse to drop the voltage down to 6 volts.

[Dobie Gillis]

The only reason they went back to 6v gauges had to have been the 12v ones weren't holding up and they were getting flack from the customers and dealers. Going back to 6v was prolly the cheapest way out.

[dmsfrr]

Originally Posted by Rusty_S85

In 55, they were 6 volt if you convert to 12 volt you need one of those 6 volt, voltage reducers attached to your power feed for your gauge cluster. this will drop the voltage at your sending units down to 6 volts as well.
In 56, they were 12 volt with no voltage reducer, my understanding is 56 was the only year ford ever ran a full 12 volts at the gauges themselves and in 57 they went to voltage regulators that pulse to drop the voltage down to 6 volts.

Because of the way the old King/Seeley gauges function, if they are an original pair, there's actually a good chance they will work on 12v.
"The fuel and temp gauges will work on 6 or 12 V and are not polarity sensitive."
(quote from this link)
https://www.ctci.org/gilsgarage/6to12.php

Originally Posted by Dobie Gillis

The only reason they went back to 6v gauges had to have been the 12v ones weren't holding up and they were getting flack from the customers and dealers. Going back to 6v was prolly the cheapest way out.

While the '57(+) dash gauges do operate on a reduced voltage Ford didn't literally 'go back' to anything. The gauge systems were redesigned to use (what I assume is) the more common resistance type.

If the gauge and sender aren't the same kind they can't talk to each other correctly.


.

[rotorwrench]

These systems work with a heater coil in the indicator. I think the idea about lowering and controlling the voltage was to keep the heat to an acceptable level to make them last longer. Even modern ones, that are still non digital nor make use of stepper motors, have a heating coil on a bi-metallic strip to make the meter move.

['46Ford]

Ok thanks all the info, kind of confusing for me as a novice to electrical systems, however I did put a reducer on the gauge, reduced to 6v. Got the reducer from Obsolete/Classic Parts. The fuel gauge read slightly over 1/2 so I filled the tank, about 6 Gals. It shows Full but the needle floats back and forth as I drive, not sure if that's normal for this car? Guess I'll watch the gauge for accuracy, any other suggestions welcome.

[KULTULZ]

Originally Posted by dmsfrr

Because of the way the old King/Seeley gauges function, if they are an original pair, there's actually a good chance they will work on 12v.

"The fuel and temp gauges will work on 6 or 12 V and are not polarity sensitive."

(quote from this link)

https://www.ctci.org/gilsgarage/6to12.php

Also read footnote from CTCI Site-

Footnote

If the 6 volt gauges do not work when the 12 volt conversion is made install a 10 ohm 10 watt wire wound resistor between the gauges and the power supply to gauges. If the gauges still do not work it may be necessary to replace the gauges and the sending units with 1956 12 volt units

__________________________


CROWN VICTORIA ASSOCIATION

6V TO 12 V CONVERSIONS-


------------


-BOB'S SPEEDOMETER-

[scicala]

On my '52 Ford (years ago) when I converted to 12 volts I used the Ford adjustable voltage reducer (as mentioned above) and adjusted it to about 6.2 volts on a 12V battery that was putting out 12.5 volts.
Then I ran the wire for fuel and temp gages from the ign. switch to the voltage reducer, and then to the gages. All worked good. The temp gage registered in the middle when is showed 180 degrees on a 2nd gage I temporarily installed.


Sal

[KULTULZ]

Maybe this can help someone-

Gauge Testing - CASCO NEWSLETTER 21 NOV 2008