1936 fuel sending unit ohms

A

aandkt

Senior Member
I am attemptong to change the Sending unit in my 1936 Cabriolet. My 36 has a 12 Volt system with a resister in front of the original dash gauge. I have cut the hole in my trunk floor thanks to help locating the sender from you guys.
I believe the correct ohms are 10 full tank and 73 empty tank.
Dennis Carpenter states the correct ohms are 17-19 full and125 full.
Can anyone set me straight on the correct OHMS and advise who sells what I need?
 
After ford switched over from the hydrostatic type gauges, They went to King Sealey gauges and senders which are all pulsed current type systems. If the fuel tank and the sending unit has been changed to rheostat based type then the gauge may have a hard time working with it.

A person may have to perform some testing on the original gauge to find out the current needs for the different positions with whatever voltage is applied. A person can do this by applying different voltages to get the meter to read empty, half full, and full, The resistance needed to drop the voltage to that required can be calculated using Ohms law.
 
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I have the original gauge and original tank. The only variable is the 12v battery and resister in front of the gauge.
 
Modern fuel gauges operate on a variable resistance method which is VERY DIFFERENT to your KING SEALEY original 36 Ford system. Your 36 Ford fuel gauge operates on a bi-metal switching on and off design in the sender unit which is very different in operation to the modern variable resistance type tank unit. The original tank units are no longer available to buy new and hard to find second hand. Whats wrong with your original sender unit. It can possibly be repaired. I have used a modern variable resistance VDO tank sender which has 15 ohms empty and approx 100 to 120 ohms full. Because the modern system works on a different principle there is no guarantee it will be accurate across the gauge full range. If you can get it to work correctly on empty then that is a good result. Check with your local VDO supplier and see what is still available. The VDO sender wont have the same fitting size where it screws into the tank. Regards, Kevin.
 
I have a 36 Tudor, is it necessary to cut a hole in the trunk floor to service the fuel sending unit?
 
Tim, there should be an oblong panel in the floor behind the rear seat to access the fuel gauge sender unit. IT slides in with a single screw at one end, Regards, Kevin.
 
A lot of the KS senders I've checked out just need the points cleaned. One point is fixed and the other is on the bi metallic strip that is manipulated by the float. The top of the sender has a cap that snaps on and off. The mechanism is small so a person has to be careful with it. There is a carbon resistor that can easily be broken and it is clipped in like a fuse. That and a wire wound resistor were used by KS to calibrate the unit at manufacter. I wouldn't mess with that stuff unless there is damage detected in there and even then there could be unrepairable damage. Repair parts don't exist so it would have to be replaced if something is damaged.
 
The sender is all messed up and looks bent. I have sent away for a replacement. I will attempt to set the float arm to show full and empty. As far as there being no hole for sender removal in the trunk, Thanks to Ford Barn members I was able to find the location where to cut a hole in my apparently replacement trunk floor. After all- That is the hobby.
Thanks to all
 
Do you have the sending unit out of the tank and have you bench tested it? It's fairly simple. Use a small 6v battery that is used for lanterns. I would make sure the orig sending unit is beyond repair before putting in the newer type. terry
 
aandkt said:
Nov 3, 2022- Still waiting for my sending unit to arrive.....
Click to expand...

Can you post a photo of your OEM sending unit along with the unit you are buying to replace it.

Please be sure to let us know how accurate the new unit is through its complete range of motion when installed with your OEM gauge.

As you already know KS units did not work on the Ohms principle so your gas tank readings with the replacement unit will be of great interest.
 
The key note is "when" I get it. One thing the old one did was stick in range of motion and the gauge never got to full.
The highest it got was to 3/4 (once) but mostly only went to 1/2 on the bench. I moved the float upand down but it did not move the gauge much. Very tight mechanism too.
 
Sorry for the lomg lapse of reply. I was in the hospital with Covid and pneumonia. It left me very week and unable to work on the '36. The Drake 12 and 6v sender is in the car but I have yet to connect the 6v Gauge. where does the reducer go?
 
I thought you stated in your first post that the voltage dropping resistor was already connected under the dash. It should be connected in line with the ignition switch controlled power wire to the gauge BAT or IGN terminal. Regards, Kevin
 
This is what a KS fuel sender looks like under the cover, which just snaps on. Dirty contact points are often the reason for not working. I had to replace the float and the corroded float arm on the one for my '46 Coupe.

Question: Does the violet band indicate it is an 8 ohm resistor?
 

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Purple generally indicates 7 ohms but with gold bands on each end, it sort of muddies the water. The 7 may just be the second digit in the code with gold being the first but gold isn't generally used for digits. It's used for percentage of tolerance only. Resistors do have a code for the colored bands but I'm not sure King Sealey followed the normal way of resistor coding. I've seen several different colors in different units but all were 6-volt system units. It may be a ballast to protect the heating coil on the bimetalic breaker point arm.

I'm sure KS used it as part of the calibration process since there are different values for the same system design used by Ford for many years. The value can be checked with an ohm meter to see if it fits the standard code or not.
 
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Why is it that when I put a 12 to 6v reducer on my 12v lead and test the output from the
other side of the reducer I still get 12v? That is the side that would go to my 6v gauge.

Will it not burn up my 6v original Ford gauge?
 
Try connecting the reducer to the gauges, and then measure the voltage.

I assume the reducer is a resistor. A resistor limits current (flow), which then reduces voltage (pressure) down-stream of the resistor. When there is no current flow, there is no voltage drop. With the gauges connected and operating there will be current, so you should be able to measure the voltage drop.
 
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