Fuel Guage driving me crazy! Help!

[75k20]

i have a 1975 k20 with dual tanks and a intellitronix electric gauge cluster. as of right now the tank selector valve doesn’t work but i have one ordered. mi just drive on my right hand tank while the left stays full.

my gas gauge is reading empty on the right side even though the tank if full.

when i switch it to the left tank it reads full which i believe is what it actually has. the gauge will slowly go between full and empty as i’m driving, and sometimes it reads somewhat at the right level.

can someone please help me figure this out? it has been driving my crazy. i just want to know how much fuel i have

 

[WP29P4A]

The first thing I would check when experiencing intermittent electrical issues is proper grounding. Most gauges use a variable resister (sender) on the ground side of the circuit to make the gauge move.

 

[75k20]

The first thing I would check when experiencing intermittent electrical issues is proper grounding. Most gauges use a variable resister (sender) on the ground side of the circuit to make the gauge move.

i’m not very good with electrical work. i cleaned up the grounds on each of the tanks. the right hand side has one from the top of the sending unit to the frame. the left hand side has a ground going from the top of the sending unit to the railing on the custom flatbed made. how could i check the variable resister?

 

[WP29P4A]

A sender just varies the resistance to move the gauge. If it wasn't in the tank it would be easier to check resistance on the sender. I know there is a way to test it with a multi meter, I have never had to test an in tank sender before. Pretty sure @SirRobyn0 will have an answer for you. I would think you measure the resistance from the sender wire to ground. But I don't know what the correct resistance range should be. I'm pretty sure if you have a direct short or open that should indicate a sender problem.

Someone who has dealt with this should comment soon and correct or confirm my opinion.

 

[75k20]

A sender just varies the resistance to move the gauge. If it wasn't in the tank it would be easier to check resistance on the sender. I know there is a way to test it with a multi meter, I have never had to test an in tank sender before. Pretty sure @SirRobyn0 will have an answer for you. I would think you measure the resistance from the sender wire to ground. But I don't know what the correct resistance range should be. I'm pretty sure if you have a direct short or open that should indicate a sender problem.

Someone who has dealt with this should comment soon and correct or confirm my opinion.

i tested for continuity between the positive and negative lead on top of my right hand tank and i got a measurement of around 10 ohms

 

[Snoots]

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[SirRobyn0]

A sender just varies the resistance to move the gauge. If it wasn't in the tank it would be easier to check resistance on the sender. I know there is a way to test it with a multi meter, I have never had to test an in tank sender before. Pretty sure @SirRobyn0 will have an answer for you. I would think you measure the resistance from the sender wire to ground. But I don't know what the correct resistance range should be. I'm pretty sure if you have a direct short or open that should indicate a sender problem.

Someone who has dealt with this should comment soon and correct or confirm my opinion.

I don't know how I missed your tag until just now, so I apologize for being late to the thread, but if you still working on this, or if someone else sees this thread they might find this info useful.

So quick gauge and wiring check. Disconnect the wire from the sending unit with the key on and the fuel gauge should go up well past the full mark to about the 3 o'clock position on the gauge. grounding out the wire from the sending unit and it should go to E. If it moves, but doesn't hit the 3 o'clock position or doesn't go to E or shoots lower than E suspect a bad resistor. There is a resistor on the back of the gauge cluster known to fail, which can cause incorrect or erratic readings. Other things can to. Next for the sending unit. The best way to test it is to remove it from the tank hook a multi-meter one end to the where the wire goes the other to the ground tab and move the sending unit arm, looking for a smooth increase and decrease in resistance change. I'm sure there is a spec, but I've never used it. If there is any rust or corrosion on the sending unit, replace it. It's 40 years old after all. Also if it seems to work correctly on one side but not the other I'd strongly suspect the sending unit or ground for that tank, possibly the tank switch.

Hopefully this helps someone and again I apologize for coming along late. I missed the notification somehow.