Sending unit issues

[Vanspeed]

Hi guys. Doing a mechanical resto only on a ‘49 F-1 that was parked for 60 years in a barn. Tank is original and good. Gas gauge is original. Sending unit is new from LMC truck. Converted to 12 volt using a Sacramento vintage ford harness. Have gauge reducers on the gauges. Fuel gauge only goes to half when full. I pulled the unit and checked it by hand to verify it was not hanging up on anything. I have good ground and if I ground the sending unit wire it pegs at full which tells me the gauge is good. Is it just a bad sending unit? Any insight appreciated.

[tubman]

Originally Posted by Vanspeed

Hi guys. Doing a mechanical resto only on a ‘49 F-1 that was parked for 60 years in a barn. Tank is original and good. Gas gauge is original. Sending unit is new from LMC truck. Converted to 12 volt using a Sacramento vintage ford harness. Have gauge reducers on the gauges. Fuel gauge only goes to half when full. I pulled the unit and checked it by hand to verify it was not hanging up on anything. I have good ground and if I ground the sending unit wire it pegs at full which tells me the gauge is good. Is it just a bad sending unit? Any insight appreciated.

Do some research on the "King-Seely" system (which Ford used) and it will all become clear. Basically, unless "LMC Truck" is a lot better than other vendors (which is doubtful), you have a mismatch between the gauge protocol and the sender protocol.

[19Fordy]

Above info. is correct. If your new sender operates on the Ohms principle it will not read accurately because the original sender and gauges in your truck did not operate on Ohms.
A search will reveal tons of information.

[Seth Swoboda]

The only way the modern sending unit will work is if you buy a modern gauge to use it with. Tubman and 19Fordy have it correct.

If you want to keep the stock gauge, you will need a NOS sending unit. Now, everytime I suggest someone find a NOS part I get a beat down on here. I have bought 4 NOS sending units in recent years with no problems.

[19Fordy]

Seth, If you ever come across a 1940 Ford 6V OEM gas tank sending unit, PLEASE let me know.
I find them to be quite rare. Thanks, JIM

[deuce lover]

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ThirdGen had one recently listed and in the orig box on Ebay ,now gone.
Here it is.Sold , 12/19/23

[JayChicago]

Originally Posted by Vanspeed

Fuel gauge only goes to half when full.

That is the opposite of what I experienced with my aftermarket sender. Your problem may be due to float arm adjustment. May be that when the float is all the way up, arm is only moving to the half way point on the sender's variable resistor. You could measure depth of tank, then on the garage floor, replicate the float and sender's movement. See if the sender's resistor is moving full range. May need to shorten the arm or bend the arm down.

You will never be able to get an aftermarket sender to work the original gauge properly over the gauge's full range. By adding resistors I finally got mine to give a proper reading near empty tank, which is where it really matters.

[19Fordy]

Originally Posted by deuce lover

ThirdGen had one recently listed and in the orig box on Ebay ,now gone.
Here it is.Sold , 12/19/23

01A-9275A is the sender used in the 1940-41 Ford cars.
01A-9275B is for 1940-41 Sedan Delivery

[Planojc]

If the sender works out of the tank but not in the tank, then I would bend the float arm down and re-install the unit and check the gauge reading. You may have to repeat this several times to get a full reading, with a full tank.

[FortyNiner]

It is possible to cobble sort of a solution with mismatched OE and repop pieces. It is not possible to get full functionality unless the pieces are designed for each other.

[Planojc]

I have a Tanks sending unit that is hooked to a 36 fuel gauge that works great.

[terry]

Originally Posted by Planojc

I have a Tanks sending unit that is hooked to a 36 fuel gauge that works great.

Where is this "Tanks" company located? Not that I am in need of a sending unit, but am just curious. Thanks, terry

[TJ]

Originally Posted by terry

Where is this "Tanks" company located? Not that I am in need of a sending unit, but am just curious. Thanks, terry

Tanks makes new gas tanks for old Fords. They are mostly sold through Yogi's in Iowa.

[Vanspeed]

Thanks for the responses. I figured it was because we are using new and old parts. I will be in the lookout for an NOS sending unit or good working original.