How to bench test a fuel gauge?

[frank8003]

Thanks. First thing I did. Why I posted a thread. Been here 4 years only posted a couple times because I can Google.

This one seems like information you seek

https://www.steelsoldiers.com/showthread.php?102692-CUCV-Fuel-gauge-issues-and-fixes

 

[OGMurph]

This is about the sender. Thanks for the info.

 

[OGMurph]

In the title BENCH TEST. I have the unit out of the cluster.

 

[frank8003]

In the title BENCH TEST. I have the unit out of the cluster.

https://www.steelsoldiers.com/showthread.php?6305-Fuel-Gauge-Diagnostic-Problem-SOLVED!

 

[OGMurph]

As I've read that thread as well because I googled it for 12 hours today. They had the sender pulled. That is also not for the same vehicle.

 

[Guyfang]

The gage you have, does it work? Have you ever seen it work? Or you want to see if it or the sending unit works? Are you electronically inclined? Or know someone who is? You can test the meter using a variable resistor. That's all the sending unit is, in essence. A variable resistor.

 

[OGMurph]

I have some electrical know how but I'm not the greatest. I've never seen the gauge work.. i've had the ground pulled on the sender and it doesn't effect the gauge.. so it could be the sender as well.. but I'm not ready to drop the tank this week.. could I Jerry rig a battery or something like that? To get the needle to jump or show a sign of life. Or death..

 

[Guyfang]

Yes, you could do that. But that still doesn't mean it's good, or accurate.

With a 5K-ohm variable resistor, (VR) you could probably test it properly. Most of the fuel gages in the military are about the same. The sending unit is a variable resistor. When a 5K VR is adjusted with a multimeter, 216-265 ohms, then hooked up to the meter, (pos side to S terminal on the meter, and neg to the G terminal) and then 24 volts applied, the meter should read about empty. When the VR is adjusted to 29.7 - 36.3, the meter should read full. The reading can be about 1/8 inch off, one way or another. I could post the whole procedure, its from a gen set, but most gages, like I say, are about the same.

 

[Coffey1]

If I remember correctly the Gage should go to full when you remove the wire from sending unit.
I know it moves one way or the other pegged full or pegged empty.
If it doesn't move the Gage is dead.

The sending unit can be checked by putting a ohm meter on the wires and moving float up and down ohms will change 0 to 13 again if I remember correctly.

 

[frank8003]

Yes, you could do that. But that still doesn't mean it's good, or accurate.

With a 5K-ohm variable resistor, (VR) you could probably test it properly. Most of the fuel gages in the military are about the same. The sending unit is a variable resistor. When a 5K VR is adjusted with a multimeter, 216-265 ohms, then hooked up to the meter, (pos side to S terminal on the meter, and neg to the G terminal) and then 24 volts applied, the meter should read about empty. When the VR is adjusted to 29.7 - 36.3, the meter should read full. The reading can be about 1/8 inch off, one way or another. I could post the whole procedure, its from a gen set, but most gages, like I say, are about the same.

Would appreciate you posting what you have from the genset. Thanks

 

[Guyfang]

All you need to do is adjust the VR to the right ohm's reading, and connect it to the meter. Apply power, and that about it. 24 VDC is applied power. Wire 137A is the positive, wire 107G is negative. The meter needs a ground, (truck would make a nice one). With a little time and wires, you can do it in the truck, or under the hood.



View attachment Übungsleiter_C_Lizens_Info0001.pdfView attachment Übungsleiter_C_Lizens_Info0002.pdf

 

[richingalveston]

cucv's are 12volt not 24.

 

[Guyfang]

Sorry!! I am a Generator guy!! But I am old enough to remember that some had dual systems? Or at least I THINK I can remember.

 

[richingalveston]

it is a dual system but all gauges work off of 12 volt. only thing that is 24 is starter so it is not like all other military trucks. just use 12 volt to test and not 24