84 gas gague problem

[72velle]

Hello folks,
trying to figure out whats wrong with the gas gague. When it works it is accurate. When it doesn't work it stays on E. It isn't consistent but mostly stays on E.
Any Ideas?
TIA!

[mongocanfly]

Sounds like loose/bad wiring or bad ground...
https://www.fillingstation.com/artic...ugetesting.htm

[Dead Parrot]

Just remember our trucks are 0-90 ohm. Says something about the original design that it survived into the 90s with minimal changes.

[Bandit130]

One thing you can try is to remove bezel, lens, light reflector, screws from gauge, clean the three prongs on back of gauge with sandpaper and then use something like alcohol. I used a slot screwdriver with sandpaper over the tip and cleaned the three clips inside, then cleaned with alcohol. Made a little difference for me, but at least they are making better contact now. The clips get rusty over the years. You may want to do all gauges that have clips.

[Palf70Step]

Normally I have found that if it is a grounding issue the guage will swing way past fuel, normally about 3 0clock position. Normally if it is on E, then there is a lack of 12V to the sender. Since it seems irratic by your description, I would check for a loose connection or broken wire to the tank sensor.

[72velle]

Thanks folks, I will let you know what I find.

[hatzie]

This is not a bad or loose sender ground.
The fuel sender is a variable resistance to ground from 0-90Ω. The fuel sender does not get power it's a passive component.

0Ω resistance through the sender makes the gauge read Empty on the gauge and 0Ω on the sender wire is a dead short to ground.
The needle randomly swinging to E means the sender wire is chafed or pinched and intermittently grounding out to the body or frame somewhere along its' run between the sender and the fuel gauge itself.

In contrast 90Ω is Full and more resistance than that drives the needle toward the 3:00 position. A completely open connection is higher resistance than 90Ω.
This is not a loose sender connection. Loose, corroded, and completely open connections cause the needle sweep to shift toward the 3:00 position. A corroded sender clip in the cluster could make the gauge read 1/8 when the tank is stone empty but it would not drive the needle toward the E position.