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Recently switched my newly acquired 53 to 12v. Changed everything but the gauge resistor ( didn't know)
When I would turn key, gauge would blast way below e. Also, ammeter was working in reverse. I reversed wires on ammeter, got a new sending unit (0-30ohm), tested it with meter first, installed the reducing resistor in pos line, and now, gauge will only read from empty to slightly below 1/4.
Took out sending unit and moved by hand, but still read up to 1/4 tank only.
Sending unit is also grounded. Ground on or off, still does same.
Anyone experience this? Did I short out gauge? Should I reverse the wires on the gauge? Thanks for any input.

Did you buy a 12V or 6V gauge? I believe both are available. Also check your old one. Often all that happens is a small wire burns off one of the coils. You can resolder it and it should work if thats the only problem.

It came with the truck. I believe it was a 6 v. I will pull it out and check the wire you refer to. Let you know how I make out. Thanks...

I ran my 6v from the factory 55.1 panel for over 100K miles after converting to 12v without messing with the gas gauge and had no issues. Try removing the resistor and see what happens.

Phil, I have exactly the same problem with my '53. When I tested it, it went quickly from empty to almost 1/4 full when the tank was full. I know the float in the tank can move freely from empty to full. I had to solder in a new wire between one of the little coils and the gauge. Still not working.

I have the same problem. Anyone have the answer?

You guys and your switching from 6V to 12V!!!! I don't know if you have a 6 or 12V gauge...a 6 or 12V sender or if it matters or if they can be mixed and matched and you got resistors and amp gauge trouble and you are reversing wires, WOW!. Listen to Tiny, it sounds like he just left the gauge and the sender as 6V. You say the sender is 0-30 Ohm and you tested it. Without getting mixed up with the other posters problems at this time, did you test the sender by itself to see if it reads 0-30 from stop to stop? Do that. Check the "search" for others who have switched to 12V and the various things they did electrically. If the gauge can take 12V and the sender can take 12V (supposedly they can according to Tiny), hook them up outside the truck on a bench with a battery charger or a battery and see if they work. If they don't work and the sender showed 0-30 ohms, when tested separately on a ohm meter, then it's a bad gauge. If they work OK, it's bad wiring hookup/reversed wires/bad ground/whatever!
To bench test the sender and gauge: Back of gauge, the terminals say the "IGN" and "SENDER", hook your power supply pos (12V) to "IGN" terminal on gauge, wire the center tap on sender to "SENDER" terminal on gauge, hook up the case of the gauge to the flange of the sender to neg of power supply. Operate float and observe gauge. Get rid of the ammeter. Put in a voltmeter. BTW: most of the time it's the grounding. You MUST have a dedicated ground wire from a sender mounting screw to nearest frame bare spot...and a good ground from gauge cluster housing to body/dash bare spot and all the other grounds necessary: batt to engine, eng to body. body to frame. (Braided straps)
You could really have a 0-90 OHM sender, your resistor could be changing the ohms the wrong way, as mentioned by Tiny or your float could be leaking

My 53 was 12 volt when I got it and fuel gage was toasted. Corrected it by hooking fuel gage to step down voltage regulator from 12 to 6 volts.
Jim Also heater was stepped down.

Here's a free how-to:
http://vintageautogarage.com/6v12vaweber.html

So yes, Bartamos, I have a 30ohm sender. Ordered brand new. Yes, I did bench test and reads form 0-30 ohms. Sender should work 6 or 12 volt, shouldn't matter. No, I'm not sure what the gauge voltage is. Looks original, but even if updated to 12' both the 6v and 12 v model that fit stock cluster are 0-30 ohm. Yes, like Tiny said, I also tried with and without resitor reducer. Yes I did reverse wires on the ammeter, but only because after converting to 12v, every time I revved gas it went down instead of up. Obviously wires were reversed when previous owner before me hooked up new autoworker factory fit harness. Now it works fine. Don't need a voltmeter. It actually acts as a voltmeter in a sense as it goes lower when lights are turned on, higher when engine is revved etc. I actually like it.
Turns out, it looks like previous owner may have had fuel gauge wires reversed as well. To what I can find out, it appears the wire to the sending unit goes on the red tag side, not the hot from ignition. So I switched them to. With power on, I read 12 volts with meter between wire that goes to sender and ground. When I bench test sender, it still reads 0-30ohms, however,I also read that if the wires on gauge are reversed that the sender will be damaged. Is this the problem even though it still reads on ohm meter? if I follow the above instructions, the gauge does go forward with key on and wire from sender grounded, suggesting a bad sender, but don't want to buy a second one if this is not the issue.

I appreciate the respones here very much and love this truck. Answering me with exclamations is like yelling thru email, or at least it seems so. I have a 56 210 that I put a big block in, ford rear, updated suspension, full wire harness, full suspension, 700r4 trans, etc. I am new to this site and apologize I cannot help too much as yet with trucks but hope to soon like on other forums pertaining to my car, but I really appreciate any help I can get here.

I also put my recent photos on my web site on my signature so you all can see my 53. Thanks for any input...Phil

The aftermarket 12volt gauge looks like this

...click...

The body is different from the original 6v