Fuel Gauge Sending Units compared

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RedFish said:
I bought a decade resistance box. Somewhere between 60 and 80 dollars, I forget. Watching a gauge respond perfectly to 1 ohm increments and factory specs doesn't help the aftermarket sender problem.
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agreed... just wanted to see if the gauge had a curve or was linear
 
If you use resistors to do some testing, make sure they are high enough wattage. At full scale, 12 volts divided by 13 + 10 ohms (gauge + sender) is about 0.5 amps. For the resistor, 0.5 amps times 10 ohms is 5 watts. A little quarter watt resistor will burn your fingers & change value after a bit. No need to ask how I know that.
 
Mike69cuda said:
make sure they are high enough wattage
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I overkilled my resisters at 100W power resistors.

UH UH UH!
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Reality... gauges run at ~6V but your point is well taken
 
Dana67Dart said:
I overkilled my resisters at 100W power resistors.

UH UH UH!
View attachment 1715463367

Reality... gauges run at ~6V but your point is well taken
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Well, I suppose it is a matter of interpretation, with the original regulator, it was a pulsed 12v, so 12 for awhile then 0 for awhile, so it averages to about 6. Math is still good, but only while it is at 12v. So on the average, you would be correct.
 
Agreed... pulsed DC we are both right ~50% of the time!:lol:
 
I just bought a new sending unit. I had to do a major rebend the fuel line so I could get it to fit into the tank. Which led to the end of it sitting higher in the tank that I am comfortable with. I left it as I think I was coming close to crimping the tube. Both the gasket and locking ring were way too small and had to reuse the parts I had just removed. I complained to the seller and he gave me a full refund, just this afternoon.

This is the 4th or 5th sending unit I have tried. They have all been abortions. But the strangest thing happened with this new sender. Before I went to the station to fill the tank, the gauge was on empty, When I finished filling the tank, that gauge was pinned to the full stop.
That is the first time, in over six years, there was a positive sign that the sender may be working properly. Keeping my fingers crossed
 
Keep a gallon in the trunk.
My old Spectra would read full for 3/4 of the tank. Then it would read 1/2 then 1/4 in about 50 miles then show empty. And you best be near a gas station
 
Dana67Dart said:
Keep a gallon in the trunk.
My old Spectra would read full for 3/4 of the tank. Then it would read 1/2 then 1/4 in about 50 miles then show empty. And you best be near a gas station
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I have always kept 2 to 3 gallons of gas in a can in the trunk. I probably always will
 
On a related subject.
Sometime soon i'll be doing a custom gauge panel with Autometer Ultra Lite gauges.
Let say the stock sending unit is 80 - 10 like the original poster said.
Several different autometer gauges are available with differing ohm ranges. The ones that are closest to 80 - 10 are.
73 - 10
and
90 - 0
Which one of these should I order ? or which would get me closest to a properly functioning fuel gauge ?
 
Dana67Dart said:
Keep a gallon in the trunk.
My old Spectra would read full for 3/4 of the tank. Then it would read 1/2 then 1/4 in about 50 miles then show empty. And you best be near a gas station
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I have a spectra in mine. I noticed the same thing as you did. With a full tank you think you're getting great gas mileage. lol. Once it reads 1/4 tank I go and fill up because it's like playing Russian roulette.

Great thread!
 
When my new spectra unit reads 1/8 of a tank it takes about 10 gallons to fill the tank. I like it that way - better to have lots of gas in the tank when the gauge reads low than the opposite!
 
My son has bought 3-4 of them, 2 were dodge trucks and 1 was a c body. All read empty when they are 1/2 full. So for a 1/2 tank it's a guessing game. Pure JUNK
 
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