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I have a 1936 Ford dual gauge for fuel and oil. The oil gauge works but the fuel gauge does not. I have a new sending unit in the tank. I know that the fuel gauge is bad. I cannot find a replacement. If anyone has ever repaired a 6 Volt fuel gauge, I would appreciate any tips, information or ideas. I want to use the original gauge.

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To check out the gauge, ground the wire to the sending unit while watching the gauge, it should go to full. If it doesn't the gauge is bad. Baxter Ford in KS repairs them and may have a replacement. The replacement sending units are not very good. If you still have your original sending unit have it repaired and use it.

[h=1]BAXTER FORD PARTS[/h] 131 ARKANSAS ST

LAWRENCE, KS 66044-1380 | view map

(785) 842-9256

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I have checked out the gage as you described and it shows the gage is good. I did this same test on a 1941 Ford gage and it showed good. On my 41 I experienced the same problem and although the test showed good, the gage was bad. I replaced the gage and it fixed the problem. I really do not think that this is an accurate test. Can't buy another 36 gage so I may send it for repair. Thank you for the information

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If you are using aftermarket sending units, you can experience this type of problem. The original sending units use a current balance to determine the fuel level. The tank unit and dash unit both have bi-metal strips wound with a heating coil. The tank unit has contact points that open and close to control the current in the dash unit. At maximum current the dash gauge moves the needle to full, with minimum current the spring in the dash gauge moves the needle to empty. The replacements try to duplicate this by using a resistive element. If the resistance in the sending unit does not fall within the range of the current used in the dash unit, the gauge will not work correctly.

Take the sending unit out of the tank and connect it to the gauge and ground the case. Operate the sending unit arm and watch the gauge. If the gauge does not move, check the reisitance of the sending unit at full and empty.

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I appreciate the information. I have also been trying to find out what the ohm range of the factory sending unit is. I would like to compare this to my replacement unit since that is my only option.

The dash gage test by shorting it out does not make much sense to me since I would only be testing full load at 6V. The gage shows good with this test but it does not show accuracy of the gage itself.

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A good original type sending unit should read near 0 ohms at all positions of the arm. An ohm meter will read the resistance of the coil wound around the bi-metal strip and the resistance of the contact points. The coil only has a few windings and will have very little resistance. The dash unit has no control over the amount that the needle moves, this is done by the sending unit. As the amount of fuel shown by the dash gauge is just an approximate value, the full current test is accurate in determining if the gauge is functional.

Here is a photo of the inside of an original type fuel sending unit. The gap in the contact points is controlled by the position of the float arm. If you do not have an original type available to you, remove the tank unit and connect it to the gauge with a jumper wire. Measure the depth of the tank and bend the arm on the sending unit to travel that distance. I like to have about 1.5" straight section near the part that moves the resister slider and then a 90 degree bend that is adjusted for the depth of the tank. Check to see that it reads full near the top and empty near the bottom. I don't have a photo of one at this time.

post-52177-143142588422_thumb.jpg

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Tony,

Again, if the needle moves on the gauge, the gauge is OK. The aftermarket sending units take quite a bit of time to get them adjusted. If you gauge needle moves when you ground the sending unit wire, and doesn't move with the aftermarket sending unit, the sending unit is not compatible with the gauge. The following description is from the 49-51 Service manual, but it applies to all King-Seeley gauges from 1936-1955.

fuel gage operation.pdf

Edited by 19tom40 (see edit history)
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  • 4 months later...

While my wife is getting ready for Thanksgiving I have been reading these old forum posts. After reading yours I went out and dug through some old stuff I didn;t use to build my 36 street rod. I did find the old sending unit and all gauges. I don't have a clue if they are good. If you are still in need they are yours. Just let me know. I rarely get on these forums, read or write, I assume your response will be e-mailed to me.

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  • 5 years later...

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