Fuel System: 1953 stude gas sender Ohms

[cobraman428]

Does anyone know the gas sender operating Ohm range for 6 volt?

Does 6v or 12V senders even matter? I know it does to the gauge. Thanks

[Jeff_H]

Here is a post of mine on this topic:

http://forum.studebakerdriversclub.com/showthread.php?51025-Bench-test-a-gas-gauge

If you are using the 6v gauges on 12v, you absolutely need a gauge voltage regulator like a Runtz, etc. The ammeter does not matter but the gas and temp do.

[brngarage]

Thanks all. I have a similar problem. Proved today (using a proper voltage dropping resistor because my '53 has been converted to 12 volts) I turned on the ignition and grounded the terminal that connects to the sender wire. Gauge moved slowly all the
way to full and returned to a little below empty when I removed the ground connection. Looks to me like a bad ground at the sender and/or a bad sender (the wiring harness is new, so the wire from gauge to sender should be OK, but I'll verify that too).

[DougHolverson]

Okay, I'm going to ask, how is a Runtz different than a reverse biased Zener?

[cobraman428]

with you asking about a reverse biased zener, sounds like you already know something about electricity. !!!!!!!!!

[52-fan]

I have a Runtz on my 52 fuel gauge, but the gauge doesn't read right. I am going to have to troubleshoot my system so your other thread is good info. I guess the Runtz device is basically a zener setup of some sort.

[Jeff_H]

I have personally not used a Runtz, but built my own equivalent using a LM317T, couple resistors, capacitors, and a diode (for blocking rev voltages). LM317 is a voltage regulator IC and I am certain it contains a zener for a reference. But, also has a series pass transistor amplifier, etc so the current capability and regulation accuracy much better than if a person tried to do this with just a zener and 1 resistor. To get good regulation with zener/resistor alone the load needs to be constant, but with the sender resistances varying as they do, that would not be likely here. Also would need to use a power zener and those are rather $$. I would have bought a runtz for my car rather than build something but I had all those parts in my stash so only my time was involved to whip it up.

[Flat Ernie]

I have personally not used a Runtz, but built my own equivalent using a LM317T, couple resistors, capacitors, and a diode (for blocking rev voltages). LM317 is a voltage regulator IC and I am certain it contains a zener for a reference. But, also has a series pass transistor amplifier, etc so the current capability and regulation accuracy much better than if a person tried to do this with just a zener and 1 resistor. To get good regulation with zener/resistor alone the load needs to be constant, but with the sender resistances varying as they do, that would not be likely here. Also would need to use a power zener and those are rather $$. I would have bought a runtz for my car rather than build something but I had all those parts in my stash so only my time was involved to whip it up.

That's awfully complicated when you could buy something like an L7806 for about $0.50 - these work great for gauges and since they're so cheap, I use one on every gauge. They provide constant 6V regardless of input voltage (the old Runtz was variable, the new appear to be electronic) and are 'cleaner' than the "choppers" used by Ford for decades and popular with hot rodders.

[thunderations]

Studebaker used the "industry standard", 33-240 Ohm. Senders are available that will be compatible with your gauge, 6 volt or 12 volt. I used a Moeller 035725-10 and bent the rod to fit my application. Works better then the replacement senders that are no longer available for my 66 and 63 Daytonas. They are available at a marine supply or on eBay. I paid around $30.

Does anyone know the gas sender operating Ohm range for 6 volt?

Does 6v or 12V senders even matter? I know it does to the gauge. Thanks

[5brown1]

Ken, Do you know what years they use the 33-240 ohm units?

[thunderations]

Not sure how many years or if forever. Studebaker usually used existing vendor parts, (cheaper then designing something different to do the same thing). This is simply a resistance to ground, no voltage or power of any sort, so you could safely connect a 33/240 sender to your sender wire and move the arm from full to empty and see what your gauge reads. Make sure you use a jumper wire from the sender flange to a good ground or it won't work at all. Give it some time in different positions as the gauge takes a little time to adjust.

Ken, Do you know what years they use the 33-240 ohm units?

[avantibngrant]

Not sure how many years or if forever. Studebaker usually used existing vendor parts, (cheaper then designing something different to do the same thing). This is simply a resistance to ground, no voltage or power of any sort, so you could safely connect a 33/240 sender to your sender wire and move the arm from full to empty and see what your gauge reads. Make sure you use a jumper wire from the sender flange to a good ground or it won't work at all. Give it some time in different positions as the gauge takes a little time to adjust.

I am curious - does anyone know what the circuitry looks like inside the gas gauge itself? My 47 Champion goes to the end and stays there even with a new sender. Sometimes it will work ok, but after while it just pegs.
I have an NOS gauge, but have not stood on my head yet to put it in.
Thanks
Neil

[TWChamp]

I am curious - does anyone know what the circuitry looks like inside the gas gauge itself? My 47 Champion goes to the end and stays there even with a new sender. Sometimes it will work ok, but after while it just pegs.
I have an NOS gauge, but have not stood on my head yet to put it in.
Thanks
Neil

Are the tank and sender well grounded? I have the tank out of my 50 Champion and the gauge goes to the end. It works fine when the tank is in place and has a good ground.

[gordr]

Studebaker gauges are "thermo" gauges. They contain two small bimetal strips wrapped with cloth-covered resistance wire, which is hair-fine. Both resistance coils have one end connected to the "IGN" terminal of the gauge. The other end of one is grounded to the case, and the other end of the second one is connected to the tank sending unit. The bimetal with its end grounded is a compensating element. It basically "reads" battery voltage, and applies force to move the pointer towards "E" as system voltage increases when the generating is charging well. The other element "reads" the current flowing through the series circuit comprised of the sending unit and itself. Full tank = minimum resistance in sender = maximum current in heating coil = bimetal bends to move pointer towards "F". Empty tank = maximum resistance of sending unit = minimum current in heating coil = bimetal bends little or not at all to leave pointer on "E". The compensating element is there to prevent the gauge from fluctuating up and down as generator output voltage varies with changes in engine speed. And I suspect it probably helps to make the gauge more accurate over a wider range of ambient temperatures.

Please note that some pre-War cars, and M-series trucks, and early 2R trucks had a fuel sending unit with TWO terminals. Both ends of the resistance element were brought out to terminals, and the moving contact, aka "wiper" was grounded, as it is in the single-terminal senders. And the gauge itself had 3 terminals, "IGN" plus one for each terminal on the sender. I have had one of those sending units apart, but NOT the corresponding gauge. I am assuming (and we all know what that means) that each bimetal element in the gauge has one end connected to "IGN", and the other to a terminal stud, and that one element acts to move the pointer towards "F", and the other acts to move it towards "E". That design would be inherently immune to to false readings caused by fluctuations in charging system voltage. I don't know if the early post-War cars had that same system, or if it was only used in the M-trucks because they were a hold-over from pre-War design, and in the early 2R's because the instrument cluster was similar to that of the M series.

But the sending unit has to be compatible with the gauge, period. Twelve volts used the 33-240 ohm range, six volts were more like 15-150 ohms. And the three-terminal jobs were something else again. You cannot mix and match gauges and sending units. To run six-volt gauges on 12 volts, the Runtz voltage reducers are the best choice, IMHO, as they made for that very purpose. A fixed series resistor is not a good choice, because the current demands of the gauge change according to how much fuel is in the tank. If you manage to make it read right at one end of the scale with a voltage-dropping resistor, it will be wrong at the other end of the scale, guaranteed. Just isn't worth the effort, when an engineered solution like the Runtz can be had by mail order.

[avantibngrant]

Thanks Gord. I was wondering if they were the heating element type we learned about in Auto shop back in the day. If I remember well, the heating of the bimetal bar was also to damp out the varying resistance at the sender from sloshing of the gas in the tank which provides a more steady reading. I put a new sender in it from SI, but there is no change. I will dig a little deeper. How are thing in Alberta?
Neil