Gas gauge - is this right?

[Southtowns27]

'46 pickup with restored gauge cluster. The gas gauge tends to read a little higher than what actually in the tank so I was experimenting with placing some low value resistors in the wire from the sending unit to the gauge to correct the reading. I was using 1 watt resistors and noticed they were getting warm. I threw the multimeter in the line and there was .72 amps flowing through the sending unit wire. That works out to almost 5 watts. That seems high to me, but maybe not?

[petehoovie]

Original gauge cluster restored? Original fuel/gas sending unit?

[Ggmac]

Why not adjust the float

[FortyNiner]

The original King Seely gauges and senders do not operate on a resistance model.

[Flathead Fever]

I agree with Ggmac, I would just bend the rod to the float. If it was an original sending unit and gauge, then it might read normal providing there was no other external resistance in the circuit. Otherwise, bend the rod.

Now if what FortyNiner said is true, I don't have clue about how a King Seely gauge works.

[Southtowns27]

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Originally Posted by FortyNiner

The original King Seely gauges and senders do not operate on a resistance model.

How do they operate? Is there a schematic kicking around?

[Ggmac]

In the old shop manuals and definitely in the green ford book .
Adjusting the the float is the easiest and best way to. You can’t mix modern resistance gauge senders with original gauges . Many tried some say they get it close . You can’t mix modern disassemble your original gauges and replace the unit with one from a late 70s ford ( they are a easy install , ) replace the needle with the old and then use a ford resistance sender .

[51woodie]

Here is a chart that may be helpful. I salvaged a King Sealy from a '51 sedan for my '46 Coupe, and I had to "play" with the float arm by bending it to get good gauge readings.

[fredM]

It's the same as adjusting the float of a toilet.

[19Fordy]

Southtown: READ ALL the info. and links in thread below telling how to adjust and fine tune your gas tank sending unit. You have to be patient.
https://www.fordbarn.com/forum/showt...k+sending+unit

[terry]

Also, if you have gone to 12v, you need a reducer to the electricity going to the guages.

[19Fordy]

Originally Posted by terry

Also, if you have gone to 12v, you need a reducer to the electricity going to the guages.

I bought a VR1 conversion unit from Ron Francis years ago.
Here's a good thread.
https://www.fordbarn.com/forum/showthread.php?t=242627

Additionally, to get an accurate reading on the 1940 Ford BATT gauge I isolated the gauge from the rest of the gauge wiring and wired it separately using a 60 ohm resistor in the 12V line that feeds only that gauge.

[Southtowns27]

Ok, I'm still running 6V. The issue I'm having is that when the tank is more than 5/8 full the needle is disappearing off the gauge way past full. Bending the float arm isn't going to correct that. I've found that my charging rate is set a bit on the high side, 7.6V. I've also since found that the gauge operates by means of a small heater that warms a bimetallic strip to cause the needle deflection, so I answered my own original question, 5W of power dissipation probably isn't off the mark. Given my slightly high system voltage (that I'm planning to leave alone since it helps headlight brightness) inserting a resistor into the sending unit line will in fact fix my issue, it just needs to be rated appropriately.

[deuce_roadster]

The KS gauges work on a frequency signal, not a voltage or resistance. The gas tank sending unit has points that create the frequency.

[19Fordy]

Make sure your gas tank sending unit float does not have a hairline crack as that will give false readings. Remove the gas tank sending unit from tank, place it on a piece of cardboard so it's insulated from all other metal. Then connect the wires from the gauge to the sending unit as you normally would BUT, run a separate ground wire from the flange on the base of the gas tank sending unit to a good ground, like the lower trunk latch.

Then manually move the float thru its arc of motion from empty to full and watch the gauge readings. If the gauge readings are inaccurate, remove the gas tank sending unit top cover with a flat screwdriver blade and turn the little starwheel a teeny weeny bit at a time. Turning it clockwise increases movement of gauge needle towards FULL. CCW moves the gauge needle towards Empty. Move your float arm thru its arc of travel after each starwheel adjustment. You may also find that you have to bend the little metal tabs on the bottom of the unit which limit its arc of travel from E to F. If you can't fix your sending unit I have a used one for sale.

If you have a 6V dry cell and a spare fuel gauge you can test your gas tank sending unit as shown below. When I check the voltage to the gas tank sending unit (with engine off and ignition switch ON) it's about 6.2 V.

[tubman]

Originally Posted by Southtowns27

Ok, I'm still running 6V. The issue I'm having is that when the tank is more than 5/8 full the needle is disappearing off the gauge way past full. Bending the float arm isn't going to correct that. I've found that my charging rate is set a bit on the high side, 7.6V. I've also since found that the gauge operates by means of a small heater that warms a bimetallic strip to cause the needle deflection, so I answered my own original question, 5W of power dissipation probably isn't off the mark. Given my slightly high system voltage (that I'm planning to leave alone since it helps headlight brightness) inserting a resistor into the sending unit line will in fact fix my issue, it just needs to be rated appropriately.

You seem to understand the King-Seeley system works. I understand what you are saying, but wouldn't turning the ignition on with the engine not running give the "true" fuel level (battery voltage only)? If the fuel value is still too high, it would seem to indicate the the high charging voltage is not the culprit. I agree with the rest here that bending the float arm is the way to fix it. Take another look at it.

[petehoovie]

Originally Posted by 51woodie

Here is a chart that may be helpful. I salvaged a King Sealy from a '51 sedan for my '46 Coupe, and I had to "play" with the float arm by bending it to get good gauge readings.

[Southtowns27]

Originally Posted by 19Fordy

Make sure your gas tank sending unit float does not have a hairline crack as that will give false readings. Remove the gas tank sending unit from tank, place it on a piece of cardboard so it's insulated from all other metal. Then connect the wires from the gauge to the sending unit as you normally would BUT, run a separate ground wire from the flange on the base of the gas tank sending unit to a good ground, like the lower trunk latch.

Then manually move the float thru its arc of motion from empty to full and watch the gauge readings. If the gauge readings are inaccurate, remove the gas tank sending unit top cover with a flat screwdriver blade and turn the little starwheel a teeny weeny bit at a time. Turning it clockwise increases movement of gauge needle towards FULL. CCW moves the gauge needle towards Empty. Move your float arm thru its arc of travel after each starwheel adjustment. You may also find that you have to bend the little metal tabs on the bottom of the unit which limit its arc of travel from E to F. If you can't fix your sending unit I have a used one for sale.

If you have a 6V dry cell and a spare fuel gauge you can test your gas tank sending unit as shown below. When I check the voltage to the gas tank sending unit (with engine off and ignition switch ON) it's about 6.2 V.

None of that applies to my truck. It has an aftermarket Bob Drake sending unit in it.

[petehoovie]

Originally Posted by Southtowns27

None of that applies to my truck. It has an aftermarket Bob Drake sending unit in it.

There's your problem...Try to find a correct King-Sealy unit...

[FortyNiner]

Originally Posted by petehoovie

There's your problem...Try to find a correct King-Sealy unit...

Exactly! The King Seely gauges and senders only play well with each other. The repop senders are not compatible with the original gauge regardless of the seller's claim.