72 dart fuel tank

[Johnny71dusty]

Sending unit was somtimes not working . Installed a new one and this one does same thing .

It has proper reistance empty and full from the post to ground . But my dash shows nothing most of the time .

My question is the blue wire at tank with plug on it . Should it have any voltage on it ? What good is resistance if there is no voltage drop to make a meter respond .

Any I missing something ?

Full my sending unit is like 9 ohms ish , Empty is like 75ohms .

The blue wire is not broken from tank to dash as I've rang it out a few times.

 

[CFD244]

I believe it should have about 5 volts. How are your other gauges working? 12 volts is stepped down to about 5 volts or so through the IVR and is used on your temp and oil pressure gauge as well as the fuel gauge. They can fail open or closed........Closed is bad news as it sends 12v through the gauges and burns them out.......That's all I got

 

[Johnny71dusty]

I believe it should have about 5 volts. How are your other gauges working? 12 volts is stepped down to about 5 volts or so through the IVR and is used on your temp and oil pressure gauge as well as the fuel gauge. They can fail open or closed........Closed is bad news as it sends 12v through the gauges and burns them out.......That's all I got

All my other gauges and dash lights work .
My blue wire : plug at the tank has no voltage

 

[Johnny71dusty]

What is Ivr ?

 

[67Dart273]

I IVR or limiter is the voltage regulation/ limit device for the gauges, which do NOT operate on full battery power

The voltage on that wire will depend on what IVR, AKA the old original OEM ones pulsed like a flasher and supplied pulsing 12V which caused an average (due to duty cycle of the pulses) of about 5--6V. The newer replacement solid state ones like RTE actually regulate 12V down to 5VDC

WHAT ARE WE working on, and DO YOU have a standard or Rallye dash, and DOES THE temp gauge and oil gauge (if present) work OK?

You should be able to ground the sender wire and cause the gauge to rocket towards the right peg with key "on." Do not leave power on for long

I don't know how you checked this, if you do not have the cluster out, check R at tank to car body. Check for proper sender/ tank grounding. Then connect wire, go up to left kick panel, separate the rear harness connector, and re-check R to ground on the sender wire.

OEM tanks were grounded via a silly clip that grabbed the sender fuel nipple, bridged the short hose a few inches, and then clipped onto the fuel tube. The idea that the tube is still grounded after 50 years is laughable.