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Where to buy a dial digital potentiometer? Sounds like that's what I need

Where to buy a dial digital potentiometer? Sounds like that's what I need

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  #1  
Old 12-03-12, 12:58 PM
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Where to buy a dial digital potentiometer? Sounds like that's what I need

Where to buy a digital potentiometer?
Sounds like that's what I need to test the sending unit on the Tahoe

The new as of yesterday fuel tank sending unit in my 1995 6.5 diesel Tahoe is not working properly. I need a potentiometer to set the ohms and see if the gauge responds accordingly
 
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  #2  
Old 12-04-12, 02:15 AM
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What did you replace......the sender or the fuel pump/sender assembly ?

What do you mean it's not working properly ?


I use a test light to ground to check the circuit.

If you want to check the actual sender out then you'll need an ohmmeter.

You could buy a potentiometer if you wanted to check the accuracy of the dash gauge but that really isn't necessary.

The fuel gauge works by supplying a certain resistance to the dash gauge based on fuel level.
When the tank is full the resistance is very low.....somewhere between 5-10 ohms.
An empty tank could be around 100 ohms. It varies by manufacturer.

So depending on where the fuel level is you'll find a resistance somewhere in between.
 
  #3  
Old 12-04-12, 06:55 AM
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The fuel pump is outside the tank on a diesel. I replaced the tank, sending unit, fuel lines and brake lines.

With 5 gallons in the tank the gauge is dived down hard below the Empty mark as soon as you hit the key. With a full tank, the gauge is at 1/2.

When you unplug the sending unit the gauge goes to full as it should. I need to check resistance with the tank full. That should tell me if it's the new AC Delco, expensive sending unit which was made in fricking china.

With a potentiometer, I can dial the ohms up and down and the gauge should reflect that. That will tell me if the gauge is bad or the wire going to the gauge
 
  #4  
Old 12-04-12, 07:13 AM
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But.....if you add a potentiometer.....all you can do is increase the resistance.

If the gauge only reads 1/2 full when the tank is full.....the accuracy will get worse.

You can't take away resistance.....which is what is required to make the gauge go up.

Sounds to me that the new sender is not the correct one for your vehicle.



.
 
  #5  
Old 12-04-12, 07:18 AM
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The part numbers all say it's the correct sending unit. I would unhook the sending unit, which in effect is a potentiometer and replace it with a potentiometer with a gauge on it. Giving me a gauge on both ends.

The gauge goes to full when the sending unit is unhooked. I haven't checked voltage to the sending unit nor do I know what the voltage is supposed to be
 
  #6  
Old 12-04-12, 07:33 AM
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Sounds more like you need to build an ohm meter calibrated to show a resistance range equal to the resistance range of your sending unit and use that as your fuel gauge.

Example only: How to Build an Ohm Meter / Mad Vapes Blog
 
  #7  
Old 12-04-12, 07:36 AM
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First I need to determine if the gauge or the sending unit are working properly

Thanks for the link!
 
  #8  
Old 12-04-12, 08:09 AM
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If you know what range of resistance your sender operates at you can use any pot from an old radio or whatever or even fixed resistors. You just need a digital ohmmeter to check the resistance value the pot is dialed to before removing the meter and connecting in line with your dash gauge. I think you really need to find the specs for your original OEM fuel sender and test the new one with an ohmmeter. Doesn't the new sender have some provision for adjustment?
 
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Old 12-04-12, 08:19 AM
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Was the gauge working properly before you replaced the tank and sender ?

If it was, then the problem is there....in the tank.
If you had a wiring problem between gauge and dash you wouldn't get any change when plugging in tank.

What comes to mind is that the float assembly was bent. I've seen that problem before.
 
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