Fuel gauge testing

[Devin]

Can I apply certain voltages to the fuel gauge to see if the needle moves on it's own? My guage is not showing changes for whatever reason and the needle feels a lot stiffer than the temp gauge. I wanted to apply power to it to test it, but there are three leads and I'm not sure what voltages cause the needle to change position.

 

[St Louis SHO]

No, the fuel gauge works by OHMs, you can put an ohm-meter on it and see if the gauge sweeps with no spikes.

 

[Devin]

Thanks, I was just about to reassemble my cluster. I'll take a look at that.

 

[Devin]

I'm doing something wrong. Neither gauges (temp and fuel) are working when I put the ohmmeter on them. There are three poles, and each set of poles give me a different reading (from about 35 to 125).

edit: So I gathered I need a 12v source to test this, but to save myself trouble Alldata reports that the slush module will turn on the low fuel indicator lamp when the signal from the sender indicates. That tells me that the the sender or the connection is bad. The needle never moves from absolute empty, and I have filled it and drained it several times.

 

[Storm-Chaser]

James [St Louis SHO] is correct. The FUEL/TEMP gauge uses resistance values provided by sensors. There are several ways to test/trouble-shoot the fuel gauge, harness, sender, etc., but require Rotunda test equipment or other comparable tester that can provide preset voltage and resistance values for testing. And if I remember correctly, there is/are tests in the Service Manual for trouble shooting instrument cluster problems.

No, the fuel gauge works by OHMs, you can put an ohm-meter on it and see if the gauge sweeps with no spikes.

I believe that the slush module as well as the printed circuit “board” on the back of the instrument cluster also need to be looked at as potential problem sources. When you get into testing the other components, not all of the tests are resistance tests, some look for circuit continuity, others for voltage-drop across the harnesses/circuits.

If you don’t have/have access to a Service Manual, let me know and I can post the test procedures from the manual.

I'm doing something wrong. Neither gauges (temp and fuel) are working when I put the ohmmeter on them. There are three poles, and each set of poles give me a different reading (from about 35 to 125).

edit: So I gathered I need a 12v source to test this, but to save myself trouble Alldata reports that the slush module will turn on the low fuel indicator lamp when the signal from the sender indicates. That tells me that the the sender or the connection is bad. The needle never moves from absolute empty, and I have filled it and drained it several times.

 

[Devin]

Can you post said test procedures? I replaced my slush module (without completely removing the cluster!) and it made no difference.

What color is the wire that runs from the sender to the cluster? All of the wires that run under the foot panel on the passenger side were cut at one point and I had to splice them back together. There is the possibility I missed that wire or it is still damaged!