View Full Version : Gas Tank Send Unit Ohms

Cowtown Commander
07-16-2013, 12:36 PM
What is the ohm range on gas tank send unit for a 1938 car? The gas gauge in my 38 Commander was not working when the restoration started. I have pulled the send unit and do not get any reading on the send unit so it is bad. Summit offers a replacement Stewart Warner send unit for under $30 but the range is 33 to 240 - is this what Studebaker used? Does voltage matter? Does it matter that 38 was positive ground? If it doesn't work for a 38 six volt positive ground, would it work for a 60 Lark 12 volt. Have looked at shop manual but they don't seem to list what the resistance range was.

Cowtown Commander

07-16-2013, 02:18 PM
Voltage matters only in the respect that different voltage sender/gauge systems use different resistances. The short answer is that you cannot mix a 12 volt sender with a 6 volt dash gauge.

Polarity, or which battery terminal is grounded, makes no difference on the type of gauges and senders in our cars.

07-16-2013, 03:36 PM
I believe it is 0-100. I found a 10-90 for my 37 and it goes from not quite empty to not quite full. I can send you some directions on how to check the ohms at your gauge when I get home Friday.

07-17-2013, 05:28 PM
Is the ohm range the same for a 41 car? My sending unit is hooped but a local hot rodder says he can fashion one to fit the existing plate if the ohm range is the same. Next question: would the ohm range be the same for a later Stude? Final question: Should things go sideways, does anyone have a gas tank sending unit for a 41 Commander (part #513163) for sale? Thanks!

07-18-2013, 12:21 AM
Be advised that some of the pre-War and early post-War cars had a different wiring system for the fuel gage than that we are used to. My '40 Champion has a two-terminal sending unit, and three-terminal dash unit. The tank unit is made with the wiper of the potentiometer grounded, and each end goes to a stud on top. Most models after 1951 or so have a single terminal sending unit, and two-terminal dash unit. Those sending units have the "full" end of the resistance winding connected to the stud, and the "empty" end is grounded, along with the wiper.

You cannot mix 6 volt and 12 volt gage components, no can you mix and match 2 and 3 terminal 6 volt components. But it may be possible to find a 2-terminal dash unit and its matching sending unit that can be adapted to fit in the instrument cluster in place of the 3-terminal one, if a new one cannot be found.