The Ford Barn

Heard · 04-17-2026, 10:16 AM

I have one of these regulators in my '35 pickup that is set up for 12v. The 6V gauge reads about 1/2 full when the tank is empty. The sending unit is from Drake that I bought along with a new fuel tank.

Can I just add some resistance to this circuit to make the gauge more accurate?

Thanks,
Heard

JayChicago · 04-17-2026, 11:33 AM

Yes. My modern aftermarket sender had the gauge needle at 1/4 when tank was empty. Was able to get it down to the E line by adding a resistor just ahead of the sender. Is still totally inaccurate at the upper end of the gauge.
Through trial and error, settled on 11 ohm resistor in my case. Each situation will be different.

But the float arm needs to be adjusted first. Arm should be able to move all the way to the bottom of its travel on the sender, just before the float bottoms out on the floor of the tank.

rotorwrench · 04-17-2026, 01:00 PM

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New types work from a rheostat variable resistor but the old ones were made by King Seeley and work off of varable current pulse principle much like the voltage regulator in the old vibrator type 3-pole regulators. When current is what operates a unit, it's in a whole different ball park than when the resistance is variable. No one makes a variable resistance sender that is calibrated to a variable current indicator. It could be done but the scales are pretty different between the two so no one takes the time to engineer one correctly.

Changing voltage of the system changes the current draw so a person needs a King Seeley 12-volt use sending unit from 1956 or later or change the indicator to a 12-volt unit depending on which way it's being modified. Those current chopper type voltage regulators work for some applications but not all. Some of them aren't the pulse type but use a modern solid state three pin voltage regulator. The Runtz units are solid state but a person needs one for each changed indicator system ie water temp, oil pressure, and fuel quantity if the vehicle has all three in King Seeley types. They just drop the voltage to 6-volts or so.

04-17-2026, 11:33 AM	#2
JayChicago Senior Member Join Date: Jan 2019 Location: Chicago Posts: 1,028	Re: Voltage regulator 12V - 6V Yes. My modern aftermarket sender had the gauge needle at 1/4 when tank was empty. Was able to get it down to the E line by adding a resistor just ahead of the sender. Is still totally inaccurate at the upper end of the gauge. Through trial and error, settled on 11 ohm resistor in my case. Each situation will be different. But the float arm needs to be adjusted first. Arm should be able to move all the way to the bottom of its travel on the sender, just before the float bottoms out on the floor of the tank.

04-17-2026, 01:00 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 18,007	Re: Voltage regulator 12V - 6V Sponsored Links (Register now to hide all advertisements) New types work from a rheostat variable resistor but the old ones were made by King Seeley and work off of varable current pulse principle much like the voltage regulator in the old vibrator type 3-pole regulators. When current is what operates a unit, it's in a whole different ball park than when the resistance is variable. No one makes a variable resistance sender that is calibrated to a variable current indicator. It could be done but the scales are pretty different between the two so no one takes the time to engineer one correctly. Changing voltage of the system changes the current draw so a person needs a King Seeley 12-volt use sending unit from 1956 or later or change the indicator to a 12-volt unit depending on which way it's being modified. Those current chopper type voltage regulators work for some applications but not all. Some of them aren't the pulse type but use a modern solid state three pin voltage regulator. The Runtz units are solid state but a person needs one for each changed indicator system ie water temp, oil pressure, and fuel quantity if the vehicle has all three in King Seeley types. They just drop the voltage to 6-volts or so. Last edited by rotorwrench; 04-17-2026 at 01:12 PM.