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I have replaced my sending unit twice. once with a used one and yesterday with a new one. My fuel gauge now is all way over the full line. is it in the cluster? did I get the wrong sending unit (twice)? I hate having to carry around a full gas can.
Any help?
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I guess the question is "did the fuel gage change its response between the used and new?" (ie. was there any difference.... as your posts seems to indicate that it NOW always reads full)... what did it read before? sounds like you have a wiring issue.
with the original sending unit it would move around a lot but usually it would stay on E. when i put in the used one and the new one, it pegged full and moved sometimes, but goes back to full.
So it's my assumption that the used one worked the same as the new one, while the original was broken. If the new one works, then it has to be something upstream. is there a known problem with the gauge? I couldn't find any reports or mentions.
Follow the wires back starting at the sender end. Sounds like a short to earth. I have tested other vehicle gauges by earthing the signal wire at the sender to make sure the gauge goes to full. On most cars the gauge will read full if you short to earth as the sender is basically a variable resistor that reduces the resistance as the float rises.
HTH
After driving for a couple of days I have a clearer picture of what is happening.
When i start the truck it peggs at full. then as I drive a while, it slowly drops to about 1/4 tank. I don't know exactly how much fuel I have currently. I will put in 8 gallons tomorrow and see what happens.
There is a module in the gauge cluster that "refines" the signal coming from the sending unit and going to the gauge. Its purpose is to take a voltage reading in increments of time and average it, then it sends a signal to the gauge. The gauge reacts to this averaged voltage. If it did not do this, then the needle would bounce all over as the gas sloshed in the tank. I would try changing this module out. I am pretty sure its cliped into the back of the gauge cluster.
Did you check the sending unit with a meter? Check the resistence on the two pins for the sending unit. You should see the value smoothly increase or decrease depending on the direction of travel of the float arm. If you see numbers jump around or an open spot, then the unit is bad.
Try this on your original and the used, see what you get.
I recently had to drop the tank to take a rusted hard brake line. I had to drop the tank to get to it. After putting it all back together my gas gauge was pegged to full. I unplugged and reseated the connection and it has worked fine since.
