12V fuel sender with 24V gauge
- Thread starter krinkov58
- Start date
suntreemcanic
Experienced Member
Yes. The gauge and sender must be matched to battery voltage.
12 volts may not be enough to give the gauge the full reading.
If you have both the sender and the gauge, just wire them, apply 12 volts and operate the sender to both extremes and see what happens.
Thanks pmuller, I'm going to...the original sender doesn't function but I have it. Was going to use a different float setup anyhow, it has a vertical tube with a float contained inside originally. If I recall correctly the sender really shouldn't care about voltage being low, it's just a resistor, like a glorified dimmer switch. I think. The gauge has a strip of metal with a heating coil that will bend it and move the needle depending on how hot the coil gets which depends on how much current the resistor in the sending unit is letting through. I think. So if the sender is sending 12V (half voltage), it should heat it to read half full?
You are correct as far as the operation. The heat being generated in the gauge is a function of wattage which is volts times amps. So if you cut your voltage in half you also cut your amperage in half giving you only one quarter of the original wattage.
Again just try it and see what you actually get.
Also remember that when the engine is running the battery is above 14 volts.
Paul
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Okay, finally getting around to getting some wiring figured out here so today I decided to test this 24V gauge so I can determine if I have to retrofit 12V guts into the housing or if I can make it work with 12V and choose a sender that will work as well.
It has a socket with 4 terminals/posts, but one is just a stud that looks as if it's for aligning the plug (stud is labeled #3 and isn't hooked up to anything according the the diagram on the side of the gauge). Wiring diagram reads #4 terminal is positive, #1 and #2 connect to terminals #1 and #2 on the original fuel tank sender (the one I have is beyond toast) and #3 terminal on sender is hooked up to negative. Gauge is from an old airplane so there's no grounding, the only thing I'm going by is a faded diagram and an old blueprint that says it's for either 12 or 24V, power consumption 0.04 Amp.
Just for giggles, I hooked up 2 AA batteries and put positive to terminal #4 and negative to terminal #1. Needle leaped to full. Kept positive on #4, moved negative to terminal #2...nothing. Decided to switch to a 9V battery now that I know the thing will work, same result. So I grabbed a 24V rheostat/dimmer switch (that is part of the original electrical system this gauge belonged to) as a substitute for a sender and this is what I got, keeping positive on terminal #4 as per diagram.
1. Terminal #1 to rheostat input, terminal #2 to rheostat output, negative to rheostat output: reads 1/3 full at 100% rheostat on, 1/4 turn down brings it to empty.
2. Terminal #1 to rheostat input, terminal #2 to rheostat output, negative to rheostat input: reads 1/3 full at 100% rheostat, 1/4 turn down brings it to full.
3. Terminal #1 to rheostat output, terminal #2 to rheostat input, negative to rheostat output: 1/3 full at 100% rheostat, 1/4 turn down brings it to full.
4. Terminal #1 to rheostat output, terminal #2 to rheostat input, negative to rheostat input: 1/3 full at 100% rheostat, 1/4 turn down brings it to empty.
So next I grabbed a spare 6V fuel tank sender from my Buick to see what would happen...I just like messing with stuff.
1. Terminal #1 to Buick sender terminal, terminal #2 to sender flange (ground), negative to sender flange: 1/3 full with float completely down, slightest movement up brings it to empty.
2. Terminal #1 to Buick sender terminal, terminal #2 to sender flange, negative to Buick sender terminal: 1/3 full with float completely down, slightest movement up brings it to full.
3. Terminal #1 to Buick sender flange, terminal #2 to Buick sender terminal, negative to sender flange: 1/3 full with float completely down, slightest movement up brings it to full.
4. Terminal #1 to Buick sender flange, terminal #2 to Buick sender terminal, negative to sender terminal: 1/3 full with float completely down, slightest movement up brings it to empty.
So I seem to be getting consistent data regarding the order of wiring, but even though the gauge will cheerfully read 100% full when directly wired with 9V or even 3V, as soon as I begin to add anything else into the circuit the best I get is 1/3 full. Granted I'm using the small gauge hobby wire with alligator clips I normally use to test things before I actually wire them up permanently so that might be part of the problem, although my direct wiring that got the gauge to read full was also the same method. So my question I guess is how to proceed...obviously with 12V and a 12V sender...but I think I'm not seeing something one of you guys might as to why the gauge will only read 1/3 full with a rheostat. Anybody?
It has a socket with 4 terminals/posts, but one is just a stud that looks as if it's for aligning the plug (stud is labeled #3 and isn't hooked up to anything according the the diagram on the side of the gauge). Wiring diagram reads #4 terminal is positive, #1 and #2 connect to terminals #1 and #2 on the original fuel tank sender (the one I have is beyond toast) and #3 terminal on sender is hooked up to negative. Gauge is from an old airplane so there's no grounding, the only thing I'm going by is a faded diagram and an old blueprint that says it's for either 12 or 24V, power consumption 0.04 Amp.
Just for giggles, I hooked up 2 AA batteries and put positive to terminal #4 and negative to terminal #1. Needle leaped to full. Kept positive on #4, moved negative to terminal #2...nothing. Decided to switch to a 9V battery now that I know the thing will work, same result. So I grabbed a 24V rheostat/dimmer switch (that is part of the original electrical system this gauge belonged to) as a substitute for a sender and this is what I got, keeping positive on terminal #4 as per diagram.
1. Terminal #1 to rheostat input, terminal #2 to rheostat output, negative to rheostat output: reads 1/3 full at 100% rheostat on, 1/4 turn down brings it to empty.
2. Terminal #1 to rheostat input, terminal #2 to rheostat output, negative to rheostat input: reads 1/3 full at 100% rheostat, 1/4 turn down brings it to full.
3. Terminal #1 to rheostat output, terminal #2 to rheostat input, negative to rheostat output: 1/3 full at 100% rheostat, 1/4 turn down brings it to full.
4. Terminal #1 to rheostat output, terminal #2 to rheostat input, negative to rheostat input: 1/3 full at 100% rheostat, 1/4 turn down brings it to empty.
So next I grabbed a spare 6V fuel tank sender from my Buick to see what would happen...I just like messing with stuff.
1. Terminal #1 to Buick sender terminal, terminal #2 to sender flange (ground), negative to sender flange: 1/3 full with float completely down, slightest movement up brings it to empty.
2. Terminal #1 to Buick sender terminal, terminal #2 to sender flange, negative to Buick sender terminal: 1/3 full with float completely down, slightest movement up brings it to full.
3. Terminal #1 to Buick sender flange, terminal #2 to Buick sender terminal, negative to sender flange: 1/3 full with float completely down, slightest movement up brings it to full.
4. Terminal #1 to Buick sender flange, terminal #2 to Buick sender terminal, negative to sender terminal: 1/3 full with float completely down, slightest movement up brings it to empty.
So I seem to be getting consistent data regarding the order of wiring, but even though the gauge will cheerfully read 100% full when directly wired with 9V or even 3V, as soon as I begin to add anything else into the circuit the best I get is 1/3 full. Granted I'm using the small gauge hobby wire with alligator clips I normally use to test things before I actually wire them up permanently so that might be part of the problem, although my direct wiring that got the gauge to read full was also the same method. So my question I guess is how to proceed...obviously with 12V and a 12V sender...but I think I'm not seeing something one of you guys might as to why the gauge will only read 1/3 full with a rheostat. Anybody?
Do you have an ohm meter?
I would like to see what the resistance is between terminals 1&2 and 2&3 on the guage.
If the positive side of the battery is connected to #4 and the negative side of the battery is connected to the Buick sender terminal which is the same as terminal #1 on the gauge, wouldn't that be the same as just connecting the battery just to the guage giving a full reading?
I'm not sure I'm getting the correct picture.
Paul
I would like to see what the resistance is between terminals 1&2 and 2&3 on the guage.
If the positive side of the battery is connected to #4 and the negative side of the battery is connected to the Buick sender terminal which is the same as terminal #1 on the gauge, wouldn't that be the same as just connecting the battery just to the guage giving a full reading?
I'm not sure I'm getting the correct picture.
Paul
pmuller9,
No I don't have an ohm meter, they're kinda pricey but I'll keep an eye on eBay...actually the #3 "terminal" isn't really a terminal, it's less than a quarter of the length of the other pins and seems to be just to align the plug in the socket, it's labeled 3 on the diagram but isn't connected to anything.
You're absolutely right in that configuration you mentioned (positive to #4, #1 to sender terminal, negative to sender terminal, #2 to flange) but it'll only act like that if I remove #2 from the flange. When #2 is re-attached to the flange the gauge jumps back from full to 1/3 full.
Here's a picture of the diagram on the side of the gauge..."Geber" mean sender, "Anzeiger" means gauge.
No I don't have an ohm meter, they're kinda pricey but I'll keep an eye on eBay...actually the #3 "terminal" isn't really a terminal, it's less than a quarter of the length of the other pins and seems to be just to align the plug in the socket, it's labeled 3 on the diagram but isn't connected to anything.
You're absolutely right in that configuration you mentioned (positive to #4, #1 to sender terminal, negative to sender terminal, #2 to flange) but it'll only act like that if I remove #2 from the flange. When #2 is re-attached to the flange the gauge jumps back from full to 1/3 full.
Here's a picture of the diagram on the side of the gauge..."Geber" mean sender, "Anzeiger" means gauge.
Attachments
It looks like the original sender used 3 connections where terminal 1 is one end of the rheostat,
terminal 2 is the wiper of the rheostat and terminal 3 is the other end.
The total resistance of the rheostat limits the current through the gauge so it reads right at full,
while the wiper of the rheostat varies the bias (Term 2 of the gauge) to make it swing from full to empty.
Does the 24 volt rheostat you first used have 3 terminals?
About what year was this gauge made?
Paul
terminal 2 is the wiper of the rheostat and terminal 3 is the other end.
The total resistance of the rheostat limits the current through the gauge so it reads right at full,
while the wiper of the rheostat varies the bias (Term 2 of the gauge) to make it swing from full to empty.
Does the 24 volt rheostat you first used have 3 terminals?
About what year was this gauge made?
Paul
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Right, terminal #3 of the original sender was negative, but isn't connected to the gauge. No the 24V rheostat only has 2 terminals (it's a light dimmer, reads "at 12 Volts 20 Watt, at 24 Volts 40 Watt" on the back). What I did today was instead of using the alligator clips on the rheostat's terminals I actually attached them and got MUCH better results, actually got it to work once by jumping the negative to one of the rheostat's terminals but couldn't replicate it, battery was dying so I quit. Will try again with 12V and better wiring.
Gauge is from late 1944-early 1945.
Edit: Pulled guts (veeery gently) out of the gauge housing to take photos
Gauge is from late 1944-early 1945.
Edit: Pulled guts (veeery gently) out of the gauge housing to take photos
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