New Gas tank sending unit problem

[71340RT]

I bought a genuine Mopar sending unit for my Cuda I'm restoring about 2 years ago. I put it in and it is a dead unit which will not make the gas gauge move. I thought the gauge was bad at first but when I ground the sending unit wire the gauges moves up to full. I put my old sending unit back in the tank and the gauge works fine. The dealer won't take the sending unit back as more 12 months have went by and I wondered if their is any fixing these units. I know they somehow work on resistance but I'm not sure what is happening inside the unit causing the gauge to change. I have took a picture of a old unit taken apart and my new unit still together. If anyone has any suggestions or ides let me know before I buy another unit. This was a bad deal as the Mopar sending units are not as cheap as the aftermarket ones are.

[hemi71]

Try grounding the new unit's case to ground...maybe it's not picking up a ground...also, check the electrical connections of the lead wire. The sending unit is just a potentimeter that is moved by the float, it changes the resistance of a variable resistor to make the gage move.

[MEK-Dangerfield]

So the old unit worked, and you are replacing it??? In any case, if you have an ohm meter, that would be helpful. Touch the meter to the pick-up tube, and that stud outside, where a blue wire would connect. If you move the float up and down, you should read something in the 10-75 ohm range.

  Mike

[Chryco Psycho]

make sure the float floats , it may not be dead just the float sunk

[71340RT]

So the old unit worked, and you are replacing it??? In any case, if you have an ohm meter, that would be helpful. Touch the meter to the pick-up tube, and that stud outside, where a blue wire would connect. If you move the float up and down, you should read something in the 10-75 ohm range.

  Mike

Mike I checked the sending unit with a ohm meter and got some strange readings. I would of used my 35 year old sending unit but it is showing it's age. I decided to take the new unit apart after I had taken a old none working unit apart and see if I could see anything wrong inside the new unit. Well the brass contact inside was bent back away from the windings it should contact so I bent it back and put it back together and guess what it now works fine. I had already put a brass float in place of he plastic one as I have already had one plastic float with a hole in it when it was brand new. Anyway thanks for the help as I really didn't want to buy another sending unit.
Jeff

[MEK-Dangerfield]

Good job Jeff.   

  Now you can become a sending unit repairman. 

  Mike