How do you test a fuel level sending unit?

#1

Could someone help me out? My fuel level gauge is reading empty and I don’t know if I have a wiring issue (very possible) or a bad sending unit. I swapped the gauge cluster to test it, but it had the same result. All other gauges work.

There are 3 pins on the sending unit.
#1 receives 12V (which I can test and see that it is being provided)
#2… IDK what this is. I assume 0-75 ohm resistance signal from what my friend says, but IDK.
#3 is ground.

Edumacate me… How can I test the sending unit and can I simulate the signal to the fuel level gauge to confirm if it’s working?

Thanks!

#2

The pin of the sensor that the Brown/Green wire goes to is the level sense pin. The pin that the Brown/Gray wires goes to is the low level switch pin. And the pin that the Brown wire goes to is the ground pin. With the sensor out of the tank, measure the resistance between the level sense pin and ground pin. With the sensor upright you should get 60ohms and the level switch pin to ground should be 0ohms. With the sensor inverted the level sense pin to ground should be 0ohms and the level switch to ground should be open circuit.

If the sensor checks out, check for continuity from the ground pin of the connector to chassis ground. Then check for continuity from the level sense pin to C2 Pin 4 at the cluster. The level switch pin of the connector goes to C2 Pin 5.

#3

Jim, if I can’t figure this out with those directions, then I will give back my engineering degree. Lol. I should’ve paid more attention in Circuits class!

#4

Turns out that I had both bad wiring between the connector and the gauge cluster, AND a bad sending unit! I rewired the connector to the cluster and am getting a sending unit tonight.

Thanks!