Fuel Gauge

[RedHot71]

Fuel gauge finally does not work at all.  Used to be it would take a second or two & it would pop up & read.  Now nothing at all.  Gauge or sending unit???

[B1B Keven]

Disconnect wires from one side of the fuel gauge and read across the two posts with an ohm meter.

You should see something between 25 and 45 ohms. If so, the gauge is good.

[peteandvanessa]

Use an ohm meter across the Fuel Sender terminals (with the wires disconnected from the Fuel Gauge).

 

You should get somewhere between 10 ohms (full) and 90 ohms (empty).

 

Then reconnect to the Fuel Sender to the Fuel gauge. You should have a wire from the ignition switch that goes to the SW terminal on the fuel gauge. When you turn on the ignition switch, you should have about 6 volts on the SW terminal. On the GA terminal on the fuel gauge you should have less that 6 volts on that terminal (the voltage will vary depending on what the fuel sender resistance is). Make sure all the terminals are clean and making a good connection.

 

You also need to make sure that there is a good ground connection on the fuel gauge itself. That ground connection relies on grounding the fuel gauge through the small mounting screws on the back of the gauge, and then the mounting screws for the actual mounting of the gauges, grounds itself to the dash. If either of those screw connections don't make a good connection to ground then the fuel gauge will read intermittently. 

[bambamshere]

I have a question about my fuel gauge/sending unit. Should there be power running from sending unit to gauge. I checked it out today with test light and the light lit up at gas tank. Should this not be grounded at the gauge and not showing power at tank. Thinking of spark at gas tank. 

[Merle Coggins]

The sending unit is a variable resistance to ground for the gauge. Voltage to the gauge and out of the gauge to the sending unit. As the level goes up the resistance gets smaller and the higher current flow will pull the needle towards the full mark. 

[bambamshere]

Thank you I took the gauge out of truck tonight and cleaned up all the.grounds on it. Probably never been done in the 64 years that it has been around. Haven't  tried it yet guess I should before I paint it. 

[Jocko_51_B3B]

I did not know that the fuel gauge needs to be grounded (should have read the service manual). My gauge quit working a while ago and I finally got around to troubleshooting it. I checked the fuel sending unit rheostat but got zero ohms in "F" position and 135 ohms in "E" which are OK. I checked the gauge and got a reading of 26 ohms across the two terminals which is good. Then I saw the comment above about grounding the gauge. When I grounded it the gauge came back to life. I added a separate ground wire for insurance to keep this from happening again. I was not able to find a fuel gage from the Pilothouse vendors I normally use. I wonder if they are still available.

Edited September 3, 2022 by Jocko_51_B3B