Erratic Fuel Gauge

[tomstin]

On my 85 325E, the fuel gauge has become a bit erratic. Sitting still, the gauge will move up or down. Most noticeable at full tank or when the fuel is getting low. Is there a way to diagnose if the problem resides in the in-tank sensor or the instrument panel?

The fuel low warning light does work when the tank gets that low.

[jbontke]

There is a ground under the dash below the gauges (bundle of brown wires), I would check it to be sure its clean and tight. If nothing changes, you can ground the sensor wire and if it holds steady, the issue is most likely the sending unit.

[tomstin]

Interesting idea, thanks!